阅读说明：本技术 一种柔性bfmo/bfco超晶格薄膜及其制备方法 (Flexible BFMO/BFCO superlattice thin film and preparation method thereof ) 是由 谈国强 奥迪 刘文龙 刘宸君 任慧君 夏傲 于 2021-07-14 设计创作，主要内容包括：本发明提供一种柔性BFMO/BFCO超晶格薄膜及其制备方法,包括：将Bi(NO-(3))-(3)·5H-(2)O、Fe(NO-(3))-(3)·9H-(2)O、C-(4)H-(6)MnO-(4)·4H-(2)O溶于溶剂中,得到前驱液A；将Bi(NO-(3))-(3)·5H-(2)O、Fe(NO-(3))-(3)·9H-(2)O、Cr(NO-(3))-(3)·9H-(2)O溶于溶剂中,得到前驱液B；在单晶氟金云母衬底上将前驱液A和前驱液B交替制膜,得到BiFe-(0.95)Mn-(0.05)O-(3/)BiFe-(0.95)Cr-(0.05)O-(3)超晶格薄膜；剥离F-Mica衬底得柔性BiFe-(0.95)Mn-(0.05)O-(3/)BiFe-(0.95)Cr-(0.05)O-(3)超晶格薄膜。所得薄膜具有优异铁磁性和各向异性磁化强度现象,且表现出优异的柔性。(The invention provides a flexible BFMO/BFCO superlattice film and a preparation method thereof, wherein the preparation method comprises the following steps: adding Bi (NO) 3 ) 3 ·5H 2 O、Fe(NO 3 ) 3 ·9H 2 O、C 4 H 6 MnO 4 ·4H 2 Dissolving O in a solvent to obtain a precursor solution A; adding Bi (NO) 3 ) 3 ·5H 2 O、Fe(NO 3 ) 3 ·9H 2 O、Cr(NO 3 ) 3 ·9H 2 Dissolving O in a solvent to obtain a precursor solution B; alternately preparing the film from the precursor solution A and the precursor solution B on the single-crystal fluorophlogopite substrate to obtain BiFe 0.95 Mn 0.05 O 3/ BiFe 0.95 Cr 0.05 O 3 SuperlatticeA film; peeling the F-Mica substrate to obtain the flexible BiFe 0.95 Mn 0.05 O 3/ BiFe 0.95 Cr 0.05 O 3 A superlattice thin film. The resulting thin film has excellent ferromagnetic and anisotropic magnetization phenomena, and exhibits excellent flexibility.)

1. A preparation method of a flexible BFMO/BFCO superlattice thin film is characterized by comprising the following steps:

step 1: adding Bi (NO)₃)₃·5H₂O、Fe(NO₃)₃·9H₂O、C₄H₆MnO₄·4H₂Dissolving O in a solvent at a molar ratio of 1.05:0.95:0.05 to obtain a precursor solution A; adding Bi (NO)₃)₃·5H₂O、Fe(NO₃)₃·9H₂O、Cr(NO₃)₃·9H₂Dissolving O in a solvent at a molar ratio of 1.05:0.95:0.05 to obtain a precursor solution B;

step 2: spin-coating the precursor solution A on a single-crystal fluorophlogopite substrate, baking at 190-220 ℃ for 8-12 min to obtain a dry film, and annealing at 540-560 ℃ for 8-10 min to obtain crystalline BiFe_0.95Mn_0.05O₃A film;

and step 3: crystalline BiFe_0.95Mn_0.05O₃Cooling the film to room temperature, and cooling the BiFe_0.95Mn_0.05O₃Spin-coating the precursor solution B on the film, baking at 190-220 ℃ for 8-12 min to obtain a dry film, and annealing at 540-560 ℃ for 8-10 min to obtain BiFe_0.95Mn_0.05O₃Preparing crystalline BiFe on the film_0.95Cr_0.05O₃A film;

and 4, step 4: repeating the step 2 and the step 3 in sequence until BiFe with the required thickness is obtained_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃A superlattice thin film;

and 5: to bear BiFe_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃Mechanically stripping the F-Mica substrate of the superlattice thin film to obtain the flexible BiFe_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃A superlattice thin film.

2. The method of claim 1, wherein in step 1, the solvent is ethylene glycol monomethyl ether and acetic anhydride.

3. The method of claim 2, wherein the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1.

4. the method for preparing a flexible BFMO/BFCO superlattice thin film according to claim 1, wherein in the precursor liquid A obtained in step 1, the concentration of metal ions is 0.15-0.25 mol/L; the concentration of metal ions in the precursor solution B is 0.15-0.25 mol/L.

5. The method for preparing a flexible BFMO/BFCO superlattice thin film according to claim 1, wherein in step 2 and step 3, spin coating is performed at a spin coating rotation speed of 3800-4000 r/min for 15-17 s.

6. The method of claim 1, wherein steps 2 and 3 are repeated 2-6 times.

7. The method of preparing a flexible BFMO/BFCO superlattice thin film according to claim 1, wherein the single crystal fluorophlogopite substrate is subjected to ultrasonic cleaning with ethanol solution and ultraviolet irradiation treatment before use.

8. A flexible BFMO/BFCO superlattice thin film as claimed in any one of claims 1 to 7 wherein said superlattice thin film contains BiFeO having space group R3c₃Bi having a space group of Pbam (55)₂Fe₄O₉Two phase structures.

Technical Field

The invention belongs to the field of functional materials, and particularly relates to flexible BiFe_0.95Mn_0.05O₃/ BiFe_0.95Cr_0.05O₃(BFMO/BFCO) superlattice thin films and methods of making the same.

Background

With the rapid development of information technology, people have developed more recent requirements such as light weight, flexibility and wearability on the basis of conventional miniaturized and highly integrated electronic components under the market demand of artificial intelligence and wearable equipment. The material is also increasingly paid more attention to as an indispensable flexible magnetic thin film material in the development process of flexible wearable electronic components. The Fe-based soft magnetic material has low coercive force, high permeability, lower loss power, easy magnetization and demagnetization and other properties and can be widely applied to devices such as sensors, converters, memories and the like, the resonance frequency of the magnetic thin film is determined by the saturation magnetization and the magnetic anisotropy field of the magnetic thin film, the resonance frequency of the magnetic thin film can be regulated and controlled by regulating and controlling the magnetic anisotropy of the magnetic thin film, the flexible thin film material with excellent anisotropic magnetization phenomenon has wide application fields and huge potential application values, can be applied to flexible wearable memories, sensors and other directions, and has attracted great research interest.

At present, most of thin film materials with anisotropic magnetization phenomenon appear in hard single crystal thin film materials, and are generally prepared by a physical method. This greatly limits the range of applications of thin film materials, especially flexible thin film materials, having the phenomenon of anisotropic magnetization.

Disclosure of Invention

The invention aims to provide a flexible BFMO/BFCO superlattice thin film and a preparation method thereof, and the obtained thin film material has excellent ferromagnetism and anisotropic magnetization phenomena and shows excellent flexibility.

The invention is realized by the following technical scheme:

a preparation method of a flexible BFMO/BFCO superlattice thin film comprises the following steps:

step 1: adding Bi (NO)₃)₃·5H₂O、Fe(NO₃)₃·9H₂O、C₄H₆MnO₄·4H₂Dissolving O in a solvent at a molar ratio of 1.05:0.95:0.05 to obtain a precursor solution A; adding Bi (NO)₃)₃·5H₂O、 Fe(NO₃)₃·9H₂O、Cr(NO₃)₃·9H₂Dissolving O in a solvent at a molar ratio of 1.05:0.95:0.05 to obtain a precursor solution B;

step 2: spin-coating the precursor solution A on a single-crystal fluorophlogopite substrate, baking at 190-220 ℃ for 8-12 min to obtain a dry film, and annealing at 540-560 ℃ for 8-10 min to obtain crystalline BiFe_0.95Mn_0.05O₃A film;

and step 3: crystalline BiFe_0.95Mn_0.05O₃Cooling the film to room temperature, and cooling the BiFe_0.95Mn_0.05O₃Spin-coating the precursor solution B on the film, baking at 190-220 ℃ for 8-12 min to obtain a dry film, and annealing at 540-560 ℃ for 8-10 min to obtain BiFe_0.95Mn_0.05O₃Preparing crystalline BiFe on the film_0.95Cr_0.05O₃A film;

and 4, step 4: repeating the step 2 and the step 3 in sequence until BiFe with the required thickness is obtained_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃A superlattice thin film;

and 5: to bear BiFe_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃Mechanically stripping the F-Mica substrate of the superlattice thin film to obtain the flexible BiFe_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃A superlattice thin film.

Preferably, in step 1, the solvent is ethylene glycol monomethyl ether and acetic anhydride.

Further, the molar ratio of ethylene glycol methyl ether to acetic anhydride is 3: 1.

preferably, in the precursor liquid A obtained in the step 1, the concentration of metal ions is 0.15-0.25 mol/L; the concentration of metal ions in the precursor solution B is 0.15-0.25 mol/L.

Preferably, in the step 2 and the step 3, spin coating is performed at a spin coating rotation speed of 3800-4000 r/min for 15-17 s.

Preferably, steps 2 and 3 are repeated 2-6 times.

Preferably, the single crystal fluorophlogopite substrate is subjected to ultrasonic cleaning with an ethanol solution and ultraviolet irradiation treatment before use.

The flexible BFMO/BFCO superlattice thin film prepared by the preparation method contains BiFeO with space group of R3c₃Bi having a space group of Pbam (55)₂Fe₄O₉Two phase structures.

Compared with the prior art, the invention has the following beneficial technical effects:

firstly, selecting fluorophlogopite single crystal as a film growth substrate, and providing a pure inorganic flexible substrate for the flexible bismuth ferrite film after the substrate is mechanically stripped; second, BiFe doped by Mn_0.95Mn_0.05O₃The phase of the layer structure is R3c space group structure BiFeO₃Phase, and Cr ion doped BiFe_0.95Cr_0.05O₃Bi with layer structure converted into Pbam (55) space group structure₂Fe₄O₉The two layers are alternately spin-coated into pure inorganic flexible BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A superlattice composite film. The film is made to have a greater preferred orientation under the influence of the two different structural interactions and the stress of the single crystal substrate, which gives it a distinct anisotropic magnetization with differences in saturation magnetization in the in-plane and out-of-plane directions. The stress effect of the single crystal mica substrate on the film influences the structure of the film, and the rotation of iron-oxygen octahedron in the bismuth ferrite is strengthened, so that the film has excellent ferromagnetic phenomenon. And the invention designs BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃Layered superlattice thin film structuresBiFe with flexibility_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃The interface layer number of the composite film material enables the flexible composite film to enhance the influence of strain engineering on the magnetism of the composite film material under the action of external mechanical bending stress/strain; and finally, the bismuth ferrite film is prepared by a chemical solution deposition method, the reaction is easy to carry out, the reaction temperature is low, the operation is easy, the bismuth ferrite film is suitable for preparing films on large surfaces and surfaces with irregular shapes, and the bismuth ferrite film is easy to grow in a preferred orientation on a fluorophlogopite single crystal substrate with smooth atomic scale.

The obtained thin film material has a significant anisotropic magnetization in which the saturation magnetization in the in-plane and out-of-plane directions differ, and an excellent ferromagnetic phenomenon.

Drawings

FIG. 1 shows BiFe prepared in example 1 of the present invention_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃XRD pattern of the composite film;

FIG. 2 is Mn doped BiFe_0.95Mn_0.05O₃XRD pattern of the layer;

FIG. 3 is Cr doped BiFe_0.95Cr_0.05O₃XRD pattern of the layer;

FIG. 4 is BiFe_0.95Mn_0.05O₃(BFMO)，BiFe_0.95Cr_0.05O₃Linear local XRD patterns of (BFCO) thin films and BFCO/BFMO superlattice thin films;

FIG. 5 shows 4 layers of BiFe prepared in example 5 of the present invention_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A thin film magnetic hysteresis loop diagram;

FIG. 6 shows 12 layers of BiFe prepared in example 1 of the present invention_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A thin film magnetic hysteresis loop diagram;

FIG. 7 shows a flexible BiFe film according to example 1 of the present invention_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A bending state diagram of the composite film;

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

Flexible BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃The preparation method of the superlattice thin film comprises the following steps:

step 1: and carrying out ultrasonic cleaning and ultraviolet irradiation on the single-crystal fluorophlogopite (F-Mica) substrate by using ethanol to obtain the hydrophilic flexible substrate.

Step 2: adding Bi (NO)₃)₃·5H₂O、Fe(NO₃)₃·9H₂O、C₄H₆MnO₄·4H₂Dissolving O in a mixed solution of ethylene glycol monomethyl ether and acetic anhydride at a molar ratio of 1.05:0.95:0.05, wherein the ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1, finally obtaining stable precursor liquid A with metal ion concentration of 0.15-0.25 mol/L; adding Bi (NO)₃)₃·5H₂O、Fe(NO₃)₃·9H₂O、Cr(NO₃)₃·9H₂Dissolving O in the mixed solution of ethylene glycol monomethyl ether and acetic anhydride in a molar ratio of 1.05:0.95:0.05 to obtain a stable precursor solution B with the metal ion concentration of 0.15-0.25 mol/L.

Step 2: spin-coating the precursor solution A on a clean F-Mica substrate at a spin-coating speed of 3800-4000 r/min for 15s, baking at 190-220 ℃ for 8-12 min to obtain a dry film after spin-coating, annealing at 540-560 ℃ for 8-10 min, and performing chemical solution deposition to obtain crystalline BiFe_0.95Mn_0.05O₃A film;

and step 3: crystalline BiFe_0.95Mn_0.05O₃Cooling the film to room temperature, and cooling the BiFe_0.95Mn_0.05O₃Spin-coating the precursor liquid B on the film at a spin-coating speed of 3800-4000 r/min for 15s, baking at 190-220 ℃ for 8-12 min after spin-coating to obtain a dry film, and annealing at 540-560 ℃ for 8-10 min to obtain BiFe_0.95Mn_0.05O₃Preparing crystalline state on filmBiFe (b) of_0.95Cr_0.05O₃A film;

and 4, step 4: repeating the steps 2 and 3 to obtain the BiFe with the required thickness_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃A superlattice thin film;

and 5: for BiFe_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃Mechanically stripping the F-Mica substrate of the superlattice thin film to obtain the flexible BiFe_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃a/F-Mica superlattice thin film.

In the step 1, the substrate is single-crystal fluorophlogopite, and the cleaning treatment of the single-crystal fluorophlogopite is ultrasonic treatment in an ethanol solution for 30min, drying for 30min and irradiation under 165nm ultraviolet light for 30min to obtain the hydrophilic flexible substrate.

In the step 4, BiFe_0.95Mn_0.05O₃And BiFe_0.95Cr_0.05O₃The thin film layers alternately grow in sequence; BiFe_0.95Mn_0.05O₃And BiFe_0.95Cr_0.05O is 2-6 layers respectively.

In the step 2 and the step 3, BiFe prepared on the single crystal fluorophlogopite substrate_0.95Mn_0.05O₃BiFeO with R3c space group structure as layer film phase₃，BiFe_0.95Cr_0.05O₃Bi with Pbam (55) space group structure as layer film phase₂Fe₄O₉。

In the step 5, the obtained superlattice BiFe_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃Controlling the thickness of the F-Mica film to be 0.04-0.008 mm by a mechanical stripping method to obtain flexible BiFe_0.95Mn_0.05O_3/BiFe_0.95Cr_0.05O₃A flexible film.

Example 1

1) Bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and C₄H₆MnO₄·4H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution A; in the obtained precursor solution A, the concentration of metal ions is 0.15 mol/L; standing the precursor solution A for 24 h; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

2) bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and Cr (NO)₃)₃·9H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution B, wherein the concentration of metal ions in the precursor solution B is 0.15 mol/L. Standing the precursor liquid B for 24 hours; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

3) and (3) spin-coating the precursor solution A on a fluorophlogopite (F-Mica) substrate by adopting a spin-coating method to prepare a wet film, wherein spin-coating adopts spin-coating at a spin speed of 3800r/min for 15 s. Baking the wet film at 190 ℃ for 8min to obtain a dry film, rapidly annealing the dry film at 540 ℃ for 10min, and cooling to room temperature to obtain single-layer BiFe_0.95Mn_0.05O₃A film.

4) BiFe obtained in step 3 by spin coating_0.95Mn_0.05O₃And spin-coating the precursor liquid B on the basis of the film to prepare a wet film, wherein spin-coating adopts spin-coating at a spin speed of 3800r/min for 15 s. Baking the wet film at 190 ℃ for 8min to obtain a dry film, rapidly annealing the dry film at 540 ℃ for 10min, and cooling to room temperature to obtain BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And (3) a layer. Then, repeating the step 3 and the step 4 in sequence, wherein the repetition frequency is 2 times; obtaining 4 layers of Bi₂Fe₄O₉/BiFeO₃A film.

5) For BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And mechanically stripping the F-Mica substrate of the film to obtain a flexible BFMO/BFCO film/F-Mica film, wherein the thickness of the F-Mica is 0.04 mm.

Example 2

1)Bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and C₄H₆MnO₄·4H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution A; in the obtained precursor solution A, the concentration of metal ions is 0.15 mol/L; standing the precursor solution A for 24 h; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

2) bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and Cr (NO)₃)₃·9H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution B; in the obtained precursor liquid B, the concentration of metal ions is 0.15 mol/L; standing the precursor liquid B for 24 hours; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

3) and (3) spin-coating the precursor solution A on a fluorophlogopite substrate by adopting a spin-coating method to prepare a wet film, wherein spin-coating adopts spin-coating at a spin speed of 3800r/min for 15 s. Baking the wet film at 190 ℃ for 8min to obtain a dry film, rapidly annealing the dry film at 540 ℃ for 8min, and cooling to room temperature to obtain single-layer BiFe_0.95Mn_0.05O₃A film.

4) And (3) spin-coating the precursor liquid B on the basis of the thin film material obtained in the step (3) by adopting a spin-coating method to prepare a wet film, wherein the spin-coating speed is 3800r/min, and the spin-coating time is 15 s. Baking the wet film at 190 ℃ for 8min to obtain a dry film, rapidly annealing the dry film at 540 ℃ for 8min, and cooling to room temperature to obtain BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And (3) a layer. Then, repeating the step 3 and the step 4 in sequence, wherein the repetition frequency is 3 times; obtaining 6 layers of BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A film.

5) For BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And mechanically stripping the F-Mica substrate of the film to obtain the flexible BFMO/BFCO/F-Mica film, wherein the thickness of the F-Mica is 0.03 mm.

Example 3

1) Bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and C₄H₆MnO₄·4H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution A; in the obtained precursor solution A, the concentration of metal ions is 0.20 mol/L; standing the precursor solution A for 24 h; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

2) bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and Cr (NO)₃)₃·9H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution B; in the obtained precursor liquid B, the concentration of metal ions is 0.20 mol/L; standing the precursor liquid B for 24 hours; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

3) and (3) spin-coating the precursor solution A on a fluorophlogopite substrate by adopting a spin-coating method to prepare a wet film, wherein spin-coating adopts spin-coating at the spin speed of 3900r/min for 16 s. Baking the wet film at 200 ℃ for 9min to obtain a dry film, rapidly annealing the dry film at 550 ℃ for 9min, and cooling to room temperature to obtain single-layer BiFe_0.95Mn_0.05O₃A film.

4) And (3) spin-coating the precursor liquid B on the basis of the thin film material obtained in the step (3) by adopting a spin-coating method to prepare a wet film, wherein the spin-coating speed is 3900r/min, and the spin-coating time is 16 s. Baking the wet film at 200 ℃ for 10min to obtain a dry film, rapidly annealing the dry film at 550 ℃ for 9min, and cooling to room temperature to obtain BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A film material. Then, repeating the step 3 and the step 4 in sequence, wherein the repetition time is 4 times; obtaining 8 layers of BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A film.

5) For BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃F-Mi of filmAnd mechanically peeling the ca substrate to obtain the flexible BFMO/BFCO/F-Mica film, wherein the thickness of the F-Mica is 0.04 mm.

Example 4

1) Bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and C₄H₆MnO₄·4H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution A; in the obtained precursor solution A, the concentration of metal ions is 0.20 mol/L; standing the precursor solution A for 24 h; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

2) bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and Cr (NO)₃)₃·9H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution B; in the obtained precursor liquid B, the concentration of metal ions is 0.20 mol/L; standing the precursor liquid B for 24 hours; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

3) and (3) spin-coating the precursor solution A on a fluorophlogopite substrate by adopting a spin-coating method to prepare a wet film, wherein spin-coating adopts spin-coating at the spin speed of 3900r/min for 16 s. Baking the wet film at 200 ℃ for 9min to obtain a dry film, rapidly annealing the dry film at 550 ℃ for 10min, and cooling to room temperature to obtain single-layer BiFe_0.95Mn_0.05O₃A film.

4) And (3) spin-coating the precursor liquid B on the basis of the thin film material obtained in the step (3) by adopting a spin-coating method to prepare a wet film, wherein the spin-coating speed is 3900r/min, and the spin-coating time is 16 s. Baking the wet film at 200 ℃ for 9min to obtain a dry film, rapidly annealing the dry film at 550 ℃ for 10min, and cooling to room temperature to obtain BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And (3) a layer. Then, repeating the step 3 and the step 4 in sequence, wherein the repetition time is 5 times; obtaining 10 layers of BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A film.

5) For BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And mechanically stripping the F-Mica substrate of the film to obtain the flexible BFMO/BFCO/F-Mica film, wherein the thickness of the F-Mica is 0.01 mm.

Example 5

1) Bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and C₄H₆MnO₄·4H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution A; in the obtained precursor solution A, the concentration of metal ions is 0.25 mol/L; standing the precursor solution A for 24 h; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

2) bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and Cr (NO)₃)₃·9H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution B; in the obtained precursor liquid B, the concentration of metal ions is 0.25 mol/L; standing the precursor liquid B for 24 hours; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

3) and (3) spin-coating the precursor solution A on a fluorophlogopite substrate by adopting a spin-coating method to prepare a wet film, wherein spin-coating adopts spin-coating at the glue-homogenizing rotating speed of 4000r/min for 17 s. Baking the wet film at 220 ℃ for 10min to obtain a dry film, rapidly annealing the dry film at 560 ℃ for 9min, and cooling to room temperature to obtain single-layer BiFe_0.95Mn_0.05O₃A film.

4) And (3) spin-coating the precursor liquid B on the basis of the thin film material obtained in the step (3) by adopting a spin-coating method to prepare a wet film, wherein the spin-coating rotation speed is 4000r/min, and the spin-coating time is 17 s. Baking the wet film at 220 ℃ for 12min to obtain a dry film, rapidly annealing the dry film at 560 ℃ for 9min, and cooling to room temperature to obtain BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And (3) a layer. Then, repeating the step 3 and the step 4 in sequence, wherein the repetition time is 6 times; obtaining 12 layers of BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A film.

5) For BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And mechanically stripping the F-Mica substrate of the film to obtain the flexible BFMO/BFCO/F-Mica film, wherein the thickness of the F-Mica is 0.02 mm.

Example 6

1) Bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and C₄H₆MnO₄·4H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution A; in the obtained precursor solution A, the concentration of metal ions is 0.25 mol/L; standing the precursor solution A for 24 h; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

2) bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and Cr (NO)₃)₃·9H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution B; in the obtained precursor liquid B, the concentration of metal ions is 0.25 mol/L; standing the precursor liquid B for 24 hours; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

3) and (3) spin-coating the precursor solution A on a fluorophlogopite substrate by adopting a spin-coating method to prepare a wet film, wherein the spin-coating adopts the spin-coating rotation speed of 4000r/min and the spin-coating time of 17 s. Baking the wet film at 220 ℃ for 11min to obtain a dry film, rapidly annealing the dry film at 560 ℃ for 9min, and cooling to room temperature to obtain single-layer BiFe_0.95Mn_0.05O₃A film.

4) And (3) spin-coating the precursor liquid B on the basis of the thin film material obtained in the step (3) by adopting a spin-coating method to prepare a wet film, wherein the spin-coating rotation speed is 4000r/min, and the spin-coating time is 17 s. Baking the wet film at 220 ℃ for 11min to obtain a dry film, rapidly annealing the dry film at 550 ℃ for 9min, and cooling to room temperature to obtain BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And (3) a layer. Then, repeating the step 3 and the step 4 in sequence, wherein the repetition frequency is 2 times; obtaining 4 layers of BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A film.

5) For BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And mechanically stripping the F-Mica substrate of the film to obtain the flexible BFMO/BFCO/F-Mica film, wherein the thickness of the F-Mica is 0.008 mm.

Example 7

1) Bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and C₄H₆MnO₄·4H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution A; in the obtained precursor solution A, the concentration of metal ions is 0.25 mol/L; standing the precursor solution A for 24 h; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

2) bi (NO) is added according to the molar ratio of 1.05:0.95:0.05₃)₃·5H₂O，Fe(NO₃)₃·9H₂O and Cr (NO)₃)₃·9H₂Dissolving O in ethylene glycol monomethyl ether, stirring for 1h, adding acetic anhydride, and continuously stirring for 1.5h to obtain a precursor solution B; in the obtained precursor liquid B, the concentration of metal ions is 0.25 mol/L; standing the precursor liquid B for 24 hours; the molar ratio of ethylene glycol monomethyl ether to acetic anhydride is 3: 1;

3) and (3) spin-coating the precursor solution A on a fluorophlogopite substrate by adopting a spin-coating method to prepare a wet film, wherein the spin-coating adopts the spin-coating rotation speed of 4000r/min and the spin-coating time of 17 s. Baking the wet film at 220 ℃ for 12min to obtain a dry film, rapidly annealing the dry film at 560 ℃ for 10min, and cooling to room temperature to obtain single-layer BiFe_0.95Mn_0.05O₃A film.

4) And (3) spin-coating the precursor liquid B on the basis of the thin film material obtained in the step (3) by adopting a spin-coating method to prepare a wet film, wherein the spin-coating rotation speed is 4000r/min, and the spin-coating time is 17 s. Baking the wet film at 220 ℃ for 12min to obtain a dry film, rapidly annealing the dry film at 560 ℃ for 10min, and cooling to room temperature to obtain BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And (3) a layer. However, the device is not suitable for use in a kitchenThen, repeating the step 3 and the step 4 in sequence, wherein the repetition frequency is 6 times; obtaining 12 layers of BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A film.

5) For BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃And mechanically stripping the F-Mica substrate of the film to obtain the flexible BFMO/BFCO/F-Mica film, wherein the thickness of the F-Mica is 0.03 mm.

The 4-layer BiFe obtained in example 1 was measured by X-ray diffractometer (XRD)_0.95Mn_0.05O₃/ BiFe_0.95Cr_0.05O₃The measurement results of the structural phases of the composite films are shown in FIG. 1. The results of XRD in FIG. 1 revealed that the phase of the obtained flexible film material contained BiFeO having space group R3c₃Bi having a space group of Pbam (55)₂Fe₄O₉Two phase structures. Diffraction peaks at 22.62 degrees, 31.96 degrees, 39.14 degrees, 51.67 degrees and 57.11 degrees in XRD belong to BiFeO₃Peaks corresponding to the (100), (110), (003), (211) and (300) planes of (A). Diffraction peaks at 14.97 degrees, 27.87 degrees, 29.96 degrees, 33.78 degrees and 66.55 degrees belong to Bi₂Fe₄O₉Peaks corresponding to (001), (121), (002), (130) and (060) planes of (c). FIGS. 2 and 3 are 12 layers of BiFe each_0.95Mn_0.05O₃Film and BiFe_0.95Cr_0.05O₃XRD analysis pattern of the thin film, FIG. 3, BiFeO induced by Cr ion doping₃Bi with space group of Pbam (55) generated by structural phase change₂Fe₄O₉Main phase, Mn doped BiFeO in XRD of FIG. 2₃The structural phase of the obtained thin film layer is still BiFeO with space group of R3c₃And (4) phase(s). FIG. 4 is BiFe_0.95Mn_0.05O₃，BiFe_0.95Cr_0.05O₃Linear local XRD patterns of the film and the BFCO/BFMO superlattice film, it can be seen that BFCO/BFMO has a preferred orientation with a larger (110) crystal plane than the BFCO and BFMO films. The composite structure promotes BiFeO₃The (110) crystal plane of (a) is preferentially oriented. BiFeO in BFCO and BFMO thin film₃The positions of the (110) peaks of (a) are 31, respectively.82 degrees 32.06 degrees, and the position (31.8 degrees) of the peak surface of the standard card (110) is shifted, so that the Mn and Cr are doped into BiFeO₃In (1).

BiFe of 4 and 12 layers obtained in example 1 and example 5 was measured using a sample vibration magnetometer (VSM) system_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃The ferromagnetic properties of the composite films were measured in the in-plane and out-of-plane directions as shown in FIGS. 5 and 6, and the ferromagnetic properties exhibited by the same sample measured in different directions were different, 4-layer BiFe_0.95Mn_0.05O₃/ BiFe_0.95Cr_0.05O₃The out-of-plane magnetization of the composite film was 3.31emn/cm³In-plane magnetization of 3.61emn/cm³And excellent ferromagnetic performance is shown. 12 layers of BiFe_0.95Mn_0.05O₃/ BiFe_0.95Cr_0.05O₃The saturation magnetization of the composite film in the in-plane direction is 0.58emn/cm³Saturation magnetization of out-of-plane direction of 0.85emn/cm³The out-of-plane saturation magnetization is 1.45 times as large as the in-plane saturation magnetization, i.e., an excellent anisotropic magnetization phenomenon is exhibited.

Through mechanical stripping of mica, the mica thickness is 0.04-0.008 mm to obtain flexible BiFe_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃The bending state diagram of the flexible film material of the/F-Mica superlattice composite film is shown in FIG. 7, the film does not crack under the bending radius of 4mm, and good flexibility is shown.

The invention successfully prepares the flexible BiFe with excellent anisotropic magnetization by adopting a simple chemical solution deposition method, selecting an inorganic nonmetallic fluorophlogopite substrate, doping magnetic transition metal ions and combining with a quasi-superlattice structure design_0.95Mn_0.05O₃/BiFe_0.95Cr_0.05O₃A superlattice thin film. The method has simple equipment requirement, easy reaching of experimental conditions and good uniformity of the prepared film.