阅读说明：本技术 一种超低磁阻尼大磁致伸缩铁氧体薄膜制备方法及系统 (Preparation method and system of ultralow-magnetic-damping giant magnetostrictive ferrite film ) 是由 刘明 王志广 胡忠强 赵亚楠 杜琴 于 2021-07-30 设计创作，主要内容包括：一种超低磁阻尼大磁致伸缩铁氧体薄膜制备方法及系统,包括以下步骤：步骤1,对镁铝尖晶石MAO衬底进行预处理,用于沉积薄膜；步骤2,将步骤1所得到的基底置于沉积腔内,进行锌/铝共掺杂镍铁氧体NZAFO的沉积工作。本发明采用脉冲激光沉积法在镁铝尖晶石(MAO)衬底上生长NZAFO单晶薄膜,系统研究了生长温度对其结构和磁性能的影响,有助于指导制备具有超低微波阻尼和大磁致伸缩的铁氧体薄膜。(A preparation method and a system of an ultra-low magnetic damping giant magnetostrictive ferrite film comprise the following steps: step 1, pretreating a magnesium aluminate spinel MAO substrate for depositing a film; and 2, placing the substrate obtained in the step 1 in a deposition chamber, and performing deposition work of the zinc/aluminum co-doped nickel ferrite NZAFO. The invention adopts a pulse laser deposition method to grow the NZAFO single crystal film on a magnesium aluminate spinel (MAO) substrate, systematically studies the influence of the growth temperature on the structure and the magnetic performance of the NZAFO single crystal film, and is favorable for guiding the preparation of the ferrite film with ultralow microwave damping and large magnetostriction.)

1. A preparation method of an ultra-low magnetic damping giant magnetostrictive ferrite film is characterized by comprising the following steps:

step 1, pretreating a magnesium aluminate spinel MAO substrate for depositing a film;

and 2, placing the pretreated substrate obtained in the step 1 in a deposition chamber, and performing deposition work of a zinc/aluminum co-doped nickel ferrite NZAFO film.

2. The method for preparing an ultra-low magnetic damping giant magnetostrictive ferrite film according to claim 1, characterized in that the pretreatment in step 1 is: ultrasonically cleaning, and drying by using nitrogen.

3. The method of claim 2, wherein the MAO single crystal substrate in step 1 is (001) -oriented and has a size of 5 x 5 mm; the substrate was ultrasonically cleaned with acetone, ethanol, and ionized water for 10 minutes, respectively.

4. The method for preparing an ultra-low magnetic damping giant magnetostrictive ferrite film according to claim 1, wherein the step 2 specifically comprises:

1) sticking and fixing the substrate on a hot table by silver glue, and placing the hot table in a reaction chamber;

2)the reaction chamber is pumped into a vacuum state by stages by using a mechanical pump and a molecular pump in sequence, and the air pressure in the reaction chamber is less than or equal to 2.5 multiplied by 10^-4When Pa is needed, the temperature is increased to the growth temperature of the film at the speed of less than or equal to 20 ℃/min, and the temperature is maintained in the process of depositing the film by laser;

3) introducing oxygen, adjusting the flow rate of the oxygen until the inlet and outlet rates of the oxygen in the reaction chamber are the same, and adjusting the air pressure of the cavity to 40 Pa;

4) preparing a film under high-energy and low-frequency laser pulses;

5) after the film deposition is finished, in-situ annealing is carried out at the film growth temperature and under the oxygen pressure, and then the temperature is reduced;

6) and after the steps are finished, naturally cooling the film in the deposition cavity.

5. The method for preparing an ultra-low magnetic damping giant magnetostrictive ferrite film according to claim 4, characterized in that the film deposition is carried out under the laser pulse with single pulse energy of 400-500 mJ and frequency of 1-3 Hz.

6. The method for preparing an ultra-low magnetic damping giant magnetostrictive ferrite film according to claim 4, characterized in that the annealing time is 10min, and the temperature is reduced to 400 ℃ at a rate of 1-10 ℃/min.

7. The method for preparing an ultra-low magnetic damping giant magnetostrictive ferrite film according to claim 1, wherein the deposition chamber in step 2 is a pulsed laser deposition chamber.

8. The method as claimed in claim 1, wherein each cation in the NZAFO spinel-type ferrite occupies A site at the center of crystal tetrahedron or B site at the center of octahedron, and the ion distribution is expressed as (M)_xFe_1-x)^A[M_1-xFe_1+x]^BO₄Wherein M is any one of the four cations of Ni, Zn, Al and Fe in NZAFO.

9. A system for preparing an ultra-low magnetic damping giant magnetostrictive ferrite film, which is characterized in that the method for preparing an ultra-low magnetic damping giant magnetostrictive ferrite film based on any one of claims 1 to 8 comprises the following steps:

the substrate pretreatment module is used for pretreating the magnesium aluminate spinel MAO substrate to obtain a deposited film;

and a deposition module, which is used for placing the substrate obtained in the step 1 into a deposition chamber to perform deposition work of the zinc/aluminum co-doped nickel ferrite NZAFO.

Technical Field

The invention belongs to the technical field of ferrite film preparation, and particularly relates to a preparation method and a system of an ultra-low magnetic damping giant magnetostrictive ferrite film.

Background

Ultra-low damping magnetic materials are critical for high frequency devices that aim to exploit the electron spin freedom. The generation of pure spin polarized current by spin pumping or spin filtering requires high performance ferromagnetic insulating materials to achieve high speed modulation and low power consumption operation.

Yttrium Iron Garnet (YIG), a damping parameter two to three orders of magnitude lower than that of ferromagnetic metals, has been widely used in microwave devices, including phase shifters, isolators, circulators, and the like. However, the complex garnet structure of YIG severely limits the selectivity of its epitaxial thin film growth, high quality YIG thin films are almost completely grown on gadolinium gallium garnet single crystal substrates and require high deposition annealing temperatures, which makes integration with the prior art problematic. In addition, YIG has a weak magnetostriction (<3ppm), which hinders its application in tunable microwave devices and acousto-spintronics. Typically, ultra-low magnetic damping requires sufficiently small spin-orbit coupling, while strong magnetostriction requires greater spin-orbit coupling, so ferromagnetic insulators with both low magnetic damping and high magnetostriction are scarce.

Recently, the zinc/aluminum co-doped nickel ferrite Ni with low damping, low coercive field and strong magnetostriction performance_0.65Zn_0.35Al_0.8Fe_1.2O₄(NZAFO) has attracted attention and is expected to be a substitute for YIG for electric field tunable microwave devices and acoustic spintronics. However, the epitaxial growth of NZAFO is limited by problems such as differences in symmetry and lattice mismatch of the thin film and substrate crystal structures, and some structural defects are inevitably introduced during the growth process. In particular, epitaxial n/n-spinel films composed of ordered cations and large cell volumes tend to form reverse phase boundaries. In addition, heat treatment and quenching also cause the crystal structure to deviate from the ideal spinel structure. The magnetic damping parameters of spinel ferrite films prepared by various methods reported at present are generally high, and the application of the spinel ferrite films in adjustable microwave equipment and spinning electronic components is limited.

Disclosure of Invention

The invention aims to provide a preparation method and a system of an ultralow-magnetic-damping giant magnetostrictive ferrite film, so as to solve the problems.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of an ultra-low magnetic damping giant magnetostrictive ferrite film comprises the following steps:

step 1, pretreating a magnesium aluminate spinel MAO substrate for depositing a film;

and 2, placing the substrate obtained in the step 1 in a deposition chamber, and performing deposition work of the zinc/aluminum co-doped nickel ferrite NZAFO.

Further, the pretreatment in the step 1 is as follows: ultrasonically cleaning, and drying by using nitrogen.

Further, the MAO single crystal substrate in step 1 was (001) -oriented, 5 x 5mm in size; the substrate was ultrasonically cleaned with acetone, ethanol, and ionized water for 10 minutes, respectively.

Further, step 2 specifically includes:

1) sticking and fixing the substrate on a hot table by silver glue, and placing the hot table in a reaction chamber;

2) the reaction chamber is pumped into a vacuum state by stages by using a mechanical pump and a molecular pump in sequence, and the air pressure in the reaction chamber is less than or equal to 2.5 multiplied by 10^-4When Pa is needed, the temperature is increased to the growth temperature of the film at the speed of less than or equal to 20 ℃/min, and the temperature is maintained in the process of depositing the film by laser;

3) introducing oxygen, adjusting the flow rate of the oxygen until the inlet and outlet rates of the oxygen in the reaction chamber are the same, and adjusting the air pressure of the cavity to 40 Pa;

4) preparing a film under high-energy and low-frequency laser pulses;

5) after the film deposition is finished, in-situ annealing is carried out at the film growth temperature and under the oxygen pressure, and then the temperature is reduced;

6) and after the steps are finished, naturally cooling the film in the deposition cavity.

Further, the deposition of the film is carried out under the laser pulse with the single pulse energy of 400-500 mJ and the frequency of 1-3 Hz.

Further, the annealing time is 10min, and the temperature is reduced to 400 ℃ at the speed of 1-10 ℃/min.

Further, the deposition chamber in the step 2 is a pulsed laser deposition chamber.

Further, each cation in the NZAFO spinel-type ferrite occupies the A site at the center of a crystal tetrahedron or the B site at the center of an octahedron, and the ion distribution is shownShown as (M)_xFe_1-x)^A[M_1-xFe_1+x]^BO₄Wherein M is any one of the four cations of Ni, Zn, Al and Fe in NZAFO.

Further, a system for preparing an ultra-low magnetic damping giant magnetostrictive ferrite film comprises:

the substrate pretreatment module is used for pretreating the magnesium aluminate spinel MAO substrate and depositing a film;

and a deposition module, which is used for placing the substrate obtained in the step 1 into a deposition chamber to perform deposition work of the zinc/aluminum co-doped nickel ferrite NZAFO.

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

the invention adopts a pulse laser deposition method to grow the NZAFO single crystal film on a magnesium aluminate spinel (MAO) substrate, systematically studies the influence of the growth temperature on the structure and the magnetic performance of the NZAFO single crystal film, and is favorable for guiding the preparation of the ferrite film with ultralow microwave damping and large magnetostriction.

The NZAFO film prepared by the invention has the line width of 7.5Oe at the lowest, and the Gilbert damping factor of 0.72 x 10^-3The film is the optimal magnetic damping parameter of the currently reported NZAFO film, has a higher magnetostriction coefficient of 12.8ppm and is more than 6 times of YIG magnetostriction coefficient, and the excellent magnetic properties are expected to promote the application of the film in high-efficiency magnetoelectric intermodulation devices and acoustic spin electronic devices.

Drawings

FIG. 1 is an X-ray diffraction (XRD) pattern of an epitaxially grown NZAFO thin film on a MAO substrate obtained in accordance with the present invention;

FIG. 2 is a hysteresis loop of an epitaxially grown NZAFO film on a MAO substrate;

FIG. 3 is a ferromagnetic resonance (FMR) spectrum of an epitaxially grown NZAFO thin film on a MAO substrate;

FIG. 4 is a Gilbert damping parameter α obtained from the frequency dependence of the linewidth of an epitaxially grown NZAFO thin film on a MAO substrate and linear fitting;

fig. 5 is a graph of magnetostriction coefficient λ of an epitaxially grown NZAFO thin film on a MAO substrate versus deposition temperature.

Detailed Description

The invention is further described below with reference to the accompanying drawings:

referring to fig. 1 to 5, a method for preparing an NZAFO thin film with ultra-low magnetic damping and large magnetostriction coefficient includes the following steps:

step 1, ultrasonically cleaning a MAO substrate by using acetone, ethanol and deionized water respectively, and then blow-drying by using nitrogen for depositing a film;

step 2, placing the substrate prepared in the step 1 in a pulsed laser deposition chamber, and performing NZAFO deposition work;

in step 1, the MAO single crystal substrate was (001) oriented, 5 x 5mm in size. The substrate is ultrasonically cleaned for 10 minutes by using acetone, ethanol and ionized water respectively to remove organic matters, metal ions and impurity microparticles adhered to the surface of the substrate, so that the subsequent deposition and growth of a film are facilitated;

the step 2 specifically comprises the following steps:

1) fixing the substrate on a hot table by silver adhesive, and placing the substrate in a reaction chamber;

2) the reaction chamber is pumped into a high vacuum state by stages by using a mechanical pump and a molecular pump in sequence, and the air pressure in the reaction chamber is less than or equal to 2.5 multiplied by 10^-4When Pa is needed, the temperature is increased to the growth temperature of the film at the speed of less than or equal to 20 ℃/min, and the temperature is maintained in the process of depositing the film by laser;

the gas environment has a great influence on the reaction, and the gas environment with insufficient purity may cause impurities or liquid droplets and small particles mixed in plasma sputtered by the laser pulse, thereby affecting the quality of the formed film. The deposition temperature and the collision rate of the growth substance are two of the most important factors in the growth process of the single crystal thin film.

3) Introducing oxygen, adjusting the flow rate of the oxygen until the inlet and outlet rates of the oxygen in the reaction chamber are the same, and adjusting the air pressure of the cavity to 40 Pa;

4) preparing a film under high-energy and low-frequency laser pulses; depositing the film under the laser pulse with the single pulse energy of 400-500 mJ and the frequency of 1-3 Hz. The high-energy laser pulse can ensure the uniformity of film formation. Because the laser pulse sputtering deposition system uses the energy with high energy, the sputtered high-energy particles also have certain directionality, and only a small-area substrate can receive the high-energy particles enough for film formation. The preparation of the film is carried out by using laser pulse (1-3 Hz) with lower frequency, so that high-energy particles falling on the surface of the substrate have enough time for epitaxial growth, and the film is favorable for forming a good crystalline phase.

5) After the film deposition is finished, in-situ annealing is carried out for 10min at the film growth temperature and under the oxygen pressure, and then the temperature is reduced to 400 ℃ at the speed of 1-10 ℃/min;

6) and after the steps are finished, naturally cooling the film in the deposition cavity.

In the invention, the substrate temperature is 450-700 ℃, the oxygen atmosphere is preferably 40Pa, the deposition frequency is preferably 3Hz, the single-pulse laser energy is preferably 450mJ, and the target base distance is preferably 6cm in the growth process of the NZAFO film;

in the present invention, each cation in the NZAFO spinel-type ferrite occupies the A site at the center of a crystal tetrahedron or the B site at the center of an octahedron, and the ion distribution can be expressed as (M)_xFe_1-x)^A[M_1-xFe_1+x]^BO₄Wherein M may be any of the four cations of Ni, Zn, Al and Fe in NZAFO. Due to the difference in growth temperature, the different occupancy patterns of Ni and Fe atoms at the a and B positions induce unquenched orbital moments and varying spin states, resulting in large changes in magnetization, magnetocrystalline anisotropy, and magnetostriction. In addition, the magnetic properties of the NZAFO thin film strongly depend on the thickness of the thin film. Therefore, the static and dynamic magnetic properties of the grown NZAFO film can be effectively regulated and controlled by changing the film deposition temperature and deposition time;

FIG. 1 is an X-ray diffraction (XRD) pattern of the NZAFO thin film obtained in this example grown epitaxially on MAO, with NZAFO (004) and MAO (004) as two diffraction peaks from left to right;

FIG. 2 is a hysteresis loop diagram of the NZAFO thin film obtained in the present example, and the saturation magnetization M of the thin film can be obtained from the relationship between the magnetization of the thin film and the intensity of the applied magnetic field_SAnd coercive force H_C；

FIG. 3 shows the NMR spectra of the NZAFO thin film obtained in this example, wherein the line width Δ H of the thin film is only 7.5 Oe;

FIG. 4 shows the variation of the ferromagnetic resonance linewidth with frequency of the NZAFO thin film obtained in this example, and the Gilbert damping parameter α of the material can be obtained by linear fitting of the NZAFO thin film as low as 0.72 × 10^-3；

Fig. 5 shows the variation of the magnetostriction coefficient with the deposition temperature for the NZAFO films prepared in this example, which have a relatively large magnetostriction coefficient (12.8 ppm at 650 c) of about 6 times or more the YIG magnetostriction coefficient.