Bi / Sm-based ordered room-temperature multiferroic double-perovskite epitaxial composite film and preparation process thereof

Abstract

The invention belongs to the field of multiferroic thin film materials, and discloses a Bi / Sm-based ordered room-temperature multiferroic double-perovskite epitaxial composite thin film and a preparation process thereof. The molecular formula of the Bi / Sm-based ordered room-temperature multiferroic double-perovskite epitaxial film is BiSmCoMeO6, and the Bi / Sm-based ordered room-temperature multiferroic double-perovskite epitaxial film is specifically prepared as follows: a second-phase controllable Co (BiMe) O4 / BiSmCoMeO6 composite film is prepared through a magnetron sputtering method under the growth conditions that the total gas flow is kept unchanged and the oxygen / argon ratio is regulated and controlled, and a Bi / Sm chemical rock salt ordered region is introduced to the BiSmCoMeO6 room-temperature multiferroic double-perovskite epitaxial film at a two-phase interface. The preparation method has the beneficial effects that on the basis that the spontaneous compositing property of the composite film is realized by regulating and controlling the sputtering deflection angle, the oxygen / argon ratio is regulated and controlled, then a spinel second phase is introduced to regulate and control the orderliness of A-site elements of the Bi / Sm-based ordered room-temperature multiferroic double-perovskite epitaxial film, and different orderliness degrees have different properties. And the development of the A-site ordered double perovskite thin film in the field of multiferroic thin films is promoted.

Description

Technical Field

[0001] The invention belongs to the field of multiferroic film materials and discloses a Bi / Sm-based ordered room temperature multiferroic double perovskite epitaxial composite film and a preparation process thereof. Background Art

[0002] Multiferroic materials refer to materials with two or more ferroic properties. Multiferroic materials are generally divided into Class I multiferroic materials and Class II multiferroic materials. Whether the microscopic origin of each ferroic property in the material is independent is an important sign to distinguish them. The multiferroic coupling of double perovskite materials is a research hotspot in the field of multiferroic films. The ordered ion arrangement and diverse element composition bring great advantages to the exploration of its multiferroic properties and make the application of high-performance double perovskite devices possible. Double perovskite film refers to a solid solution film material formed by two single perovskite structure materials in a 1:1 ratio. Element order and stoichiometric ratio (about 1) are necessary conditions for the formation of double perovskite films, among which element order is a necessary requirement for significantly improving the multiferroic properties of double perovskite films. Therefore, finding an ordered double perovskite film that meets the stoichiometric ratio of double perovskite is a research difficulty in this field. Exploring the order conditions of double perovskite films is one of the important issues that researchers must solve.

[0003] So far, researchers at home and abroad have conducted in-depth research on B-site ordered double perovskite multiferroic films, especially double perovskite films mainly ordered by transition metals, such as Fe / Cr order, Fe / Mn order, etc. However, the conditions for their ordered preparation have not been explored. In addition, the study of the order of A-site double perovskite room temperature multiferroic films is an important part missing in this field. Summary of the invention

[0004] The invention discloses a Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film and a preparation process thereof, so as to solve any of the above and other potential problems of the prior art.

[0005] To achieve the above-mentioned purpose, the technical solution of the present invention is: a Bi / Sm-based room-temperature multiferroic ordered double perovskite epitaxial composite film, which is grown on a single crystal substrate, and the molecular structure of the Bi / Sm-based room-temperature multiferroic ordered double perovskite epitaxial composite film is: Co(BiMe)O4 / BiSmCoMeO6.

[0006] Furthermore, the crystal structure of the Bi / Sm-based ordered room temperature multiferroic double perovskite epitaxial composite film includes an orthorhombic phase and a second phase, and the space group of the orthorhombic phase is Pbnm, and the degree of order is 30%-65%.

[0007] Furthermore, the A-site elements Bi and Sm of the Bi / Sm-based ordered room-temperature multiiron double perovskite epitaxial composite film have chemical rock salt order, and the chemical rock salt ordered region of Bi and Sm exists at the interface between the orthorhombic phase and the second phase.

[0008] Furthermore, the second phase is a cubic spinel structure, and the chemical formula of the spinel structure is Co(BiMe)O4.

[0009] Furthermore, the Me is one of the transition metal elements Fe, Co, Mn and Ni.

[0010] Furthermore, the single crystal substrate is SrTiO3 or Nb-SrTiO3.

[0011] Another object of the present invention is to provide a process for preparing the above-mentioned Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film, the process comprising the following steps:

[0012] S1) selecting a single crystal substrate as a substrate, washing it, drying it naturally, and placing it in a sample sputtering platform;

[0013] S2) prepare a Bi / Sm-based ceramic target and place it in a magnetron sputtering platform. After heating, use radio frequency magnetron sputtering preparation technology to deposit a thin film to obtain a Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film.

[0014] Further, the radio frequency magnetron sputtering preparation technology in S2) is specifically: the vacuum is 1×10 -5 Torr, the oxygen / argon ratio is 0.1-8:10-2, the sputtering angle is 32.5°-34.0°, the total gas flow rate is 9-11sccm, the working gas pressure is 0.4-0.8Pa, the RF power is 60-120W, and the deposition time is 0.1-4.0 hours.

[0015] Furthermore, the obtained Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film has room temperature ferroelectricity, and the saturated ferroelectric polarization is 15.0-25.0 μC / cm 2 .

[0016] Furthermore, the obtained Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film has room temperature ferromagnetism, and the saturation magnetization intensity is 9.0-11.0emu / cm 3 .

[0017] Furthermore, the crystal plane orientation of the single crystal substrate is (001), and the specific size is 5×5×0.3 mm 3 or 10×10×0.3mm 3 .

[0018] In summary, the present invention includes at least one of the following beneficial technical effects:

[0019] 1. The present invention provides a method for preparing Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial thin films based on magnetron sputtering.

[0020] 2. The present invention provides a method for regulating the order of A-site elements (Bi and Sm) in Bi / Sm-based ordered room-temperature multiiron double perovskite epitaxial films based on magnetron sputtering.

[0021] 3. The present invention realizes the spontaneous recombination of spinel and orthorhombic phase in the film by regulating the sputtering deflection angle. The spontaneous recombination of spinel / orthorhombic phase only occurs during the deposition process of the double perovskite film.

[0022] 4. The present invention regulates the spontaneous recombination of the composite film by regulating the sputtering deflection angle, and regulates the order of the A-site elements of the Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial film by regulating the oxygen / argon ratio and introducing the spinel second phase, and different ordering degrees should have different properties. Among them, as the oxygen / argon ratio increases, the spinel second phase decreases, and the ordering degree of the Bi / Sm-based room temperature multi-iron double perovskite epitaxial film decreases.

[0023] 5. The present invention can control the A-site order of Bi / Sm-based room temperature multiferroic double perovskite epitaxial films, thereby regulating the multiferroic properties of the films, such as ferroelectricity and ferromagnetism. This has promoted the development of A-site ordered double perovskite films in the field of multiferroic films. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the crystal structure of the Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film and its preparation process of the present invention.

[0025] Figure 2 This is the (001) XRD pattern of the ordered BiSmCoFeO6 double perovskite epitaxial composite film deposited on a SrTiO3 substrate according to the present invention, with the oxygen / argon ratio controlled at 2:8-6:4. The diffraction peak of the spinel second phase is marked with "◆".

[0026] Figure 3 This is the (111) XRD pattern of the ordered BiSmCoFeO6 double perovskite epitaxial composite film deposited on a SrTiO3 substrate according to the present invention, with the oxygen / argon ratio controlled at 2:8-6:4. The diffraction peak of the spinel second phase is marked with “◆”.

[0027] Figure 4This is the (001) XRD pattern of the ordered BiSmCoFeO6 double perovskite epitaxial composite film deposited on the Nb-SrTiO3 substrate of the present invention, with the oxygen / argon ratio controlled at 2:8-6:4. The diffraction peak of the spinel second phase is marked with "◆".

[0028] Figure 5 This is the (001) XRD pattern of the ordered BiSmCo2O6 double perovskite epitaxial composite film deposited on a SrTiO3 substrate according to the present invention, with the oxygen / argon ratio controlled at 1:9. The diffraction peak of the spinel second phase is marked with “◆”.

[0029] The atomic phase diagram of the dark phase indicates the chemical order between the A-site elements Bi / Sm in the film.

[0030] Figure 6 This is the

[100] axial STEM atomic phase image of the ordered BiSmCoFeO6 double perovskite epitaxial composite film deposited on a SrTiO3 substrate according to the present invention.

[0031] Figure 7 The phase diagram of temperature-oxygen-argon ratio-phase structure of the ordered BiSmCoFeO6 double perovskite epitaxial composite film described in the present invention.

[0032] Figure 8 Schematic diagram of the hysteresis loop of the ordered BiSmCoFeO6 double perovskite epitaxial composite film described in the present invention.

[0033] Fig. 9 Schematic diagram of the hysteresis loop of the ordered BiSmCoFeO6 double perovskite epitaxial composite film described in the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, a Bi / Sm-based ordered room-temperature multiferroic double perovskite epitaxial composite film based on magnetron sputtering is invented, the structure of the epitaxial film includes a substrate and a Bi / Sm-based ordered room-temperature multiferroic double perovskite epitaxial composite film epitaxially grown on the substrate, the substrate is a single crystal substrate, and the crystal structure of the Bi / Sm-based ordered room-temperature multiferroic double perovskite epitaxial composite film is an orthorhombic phase and a spinel phase.

[0036] The A-site elements of the Bi / Sm-based ordered room-temperature multi-iron double perovskite epitaxial composite film are Sm and Bi, the B-site elements are Co and Me, and the chemical formula of the film is Co(BiMe)O4 / BiSmCoMeO6.

[0037] The film contains chemical rock salt ordered regions of the elements Bi and Sm.

[0038] The chemical rock-salt ordered region of the elements Bi and Sm exists at the interface with the spinel second phase.

[0039] The Me is one of the transition metal elements Fe, Co, Mn and Ni.

[0040] The single crystal substrate is SrTiO3 or Nb-SrTiO3.

[0041] A process for preparing the above-mentioned Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial film by magnetron sputtering, the process comprising the following steps:

[0042] S1) selecting a single crystal substrate as a substrate, washing it, drying it naturally, and placing it in a sample sputtering platform;

[0043] S2) prepare a Bi / Sm-based ceramic target and place it in a magnetron sputtering platform. After heating, a radio frequency magnetron sputtering preparation technology is used to deposit a thin film, thereby obtaining a Bi / Sm-based room temperature multi-iron ordered double perovskite epitaxial composite film, such as Figure 2 As shown;

[0044] The single crystal substrate has a crystal plane orientation of (001) and a specific size of 5×5×0.3 or 10×10×0.3 mm. 3 .

[0045] The oxygen / argon ratio in the film preparation process in S2) is 0.1-8:10-2.

[0046] The specific process of the radio frequency magnetron sputtering preparation technology is:

[0047] In vacuum, 1×10 -5 -3×10 -5 Torr, the sputtering angle is 32.5°-34.0°, the oxygen / argon ratio is 0.1-8:10-2, the total gas flow rate is 9-11sccm, the working gas pressure is 0.4-0.8Pa, the RF power is 60-120W, and the deposition time is 0.5-4.0 hours.

[0048] The obtained Bi / Sm-based ordered room temperature multiferroic double perovskite epitaxial composite film has room temperature ferroelectricity, and the saturated ferroelectric polarization is 20.0-25.0 μC / cm 2 ,like Figure 8 shown.

[0049] The obtained Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film has room temperature ferromagnetism, and the saturation magnetization intensity is 9.0-11.0emu / cm 3 ,like Fig. 9 shown.

[0050] The Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film has a thickness of 20-200 nm.

[0051] During the preparation of the Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film, the average sputtering rate is

[0052] The Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film can effectively control the order of its A-position elements (Bi and Sm) when the oxygen / argon ratio in the film preparation process is 0.1-8:10-2.

[0053] When the oxygen / argon ratio is higher than 6:4, the ordered phase in this type of film disappears, e.g. Figure 7 shown.

[0054] The Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film cannot be deposited with high quality when the deposition temperature is lower than 500°C. Figure 7 shown.

[0055] Embodiment 1:

[0056] The powders of Bi2O3, Sm2O3, Fe2O3 and Co2O3 with a molar ratio of 1.15:1:1:1 were uniformly mixed to prepare a target material for use; the (001)-SrTiO3 single crystal substrate was placed on the sample platform of the magnetron sputtering instrument, and the off-axis sputtering angle was adjusted to 33°; then the background vacuum was reduced to 1×10 -5 Torr, while maintaining the deposition temperature at 575℃; then introduce Ar and O2 into the magnetron sputtering chamber, ensuring that the Ar / O2 flow ratio is 8:2, the gas flow rate is 10sccm, and the working pressure is 0.4Pa; then provide 90W RF power to the target, and after deposition for 3.0h, a 120nm thick high-quality Co(BiFe)O4 / BiSmCoFeO6 ordered room temperature multi-iron double perovskite epitaxial composite film is obtained. Its (001) XRD is shown in the attached Figure 2 As shown in Figure 2, only the diffraction peaks of the spinel second phase, the orthorhombic phase ordered film and the substrate are present, indicating the epitaxial nature of the film. With the increase of the oxygen / argon ratio, the spinel second phase gradually disappears. Its (111) XRD pattern is shown in Figure 2. Figure 3 As shown in Figure 2, the existence of the sp super-diffraction peak indicates the chemical order of the film, with an order degree of 60%. Its STEM atomic phase diagram is shown in Figure 2. Figure 6 As shown in the figure, there are light and dark atoms at the junction of the spinel second phase and the orthorhombic phase, which also shows the chemical order of the film. And for this film, we obtained 22.8μC / cm in the multiferroic performance test.2 The polarization intensity and 11.5emu / cm 3 The magnetization intensity, such as Figure 8 , 9 shown.

[0057] Embodiment 2:

[0058] The powders of Bi2O3, Sm2O3, Fe2O3 and Co2O3 with a molar ratio of 1.15:1:1:1 were uniformly mixed to prepare a target material for use; the (001)-SrTiO3 single crystal substrate was placed on the sample platform of the magnetron sputtering instrument, and the off-axis sputtering angle was adjusted to 33°; then the background vacuum was reduced to 1×10 -5 Torr, while maintaining the deposition temperature at 575℃; then Ar and O2 were introduced into the magnetron sputtering chamber, ensuring that the Ar / O2 flow ratio was 4:6, the gas flow rate was 10sccm, and the working pressure was 0.4Pa; then 90W RF power was provided to the target material, and after deposition for 3.0h, a 120nm thick high-quality Co(BiFe)O4 / BiSmCoFeO6 ordered room temperature multi-iron double perovskite epitaxial composite film was obtained, with an order degree of 30%. Its (001) XRD is shown in the attached Figure 2 As shown in the figure, there are only diffraction peaks of the orthorhombic phase film and the substrate, indicating the epitaxial nature of the film; its (111) XRD is shown in the attached Figure 3 As shown in Figure 2, the existence of the sp superdiffraction peak indicates the chemical order of the film. In addition, for this film, we obtained 15.0 μC / cm in the multiferroic performance test. 2 The polarization intensity.

[0059] Embodiment 3:

[0060] The powders of Bi2O3, Sm2O3, Fe2O3 and Co2O3 with a molar ratio of 1.15:1:1:1 were uniformly mixed to prepare a target material for use; the (001)-SrTiO3 single crystal substrate was placed on the sample platform of the magnetron sputtering instrument, and the off-axis sputtering angle was adjusted to 33°; then the background vacuum was reduced to 1×10 -5 Torr, while maintaining the deposition temperature at 575℃; then Ar and O2 were introduced into the magnetron sputtering chamber to ensure that the Ar / O2 flow ratio was 6:4, the gas flow rate was 10sccm, and the working pressure was 0.4Pa; then 90W RF power was provided to the target material. After deposition for 3.0h, a 120nm thick high-quality Co(BiFe)O4 / BiSmCoFeO6 ordered room temperature multi-iron double perovskite epitaxial composite film was obtained with an order degree of 45%. Its (001) XRD is shown in the attached Figure 2 As shown in Figure 2, only the diffraction peaks of the spinel second phase, the orthorhombic phase ordered film and the substrate are present, indicating the epitaxial nature of the film. Figure 3 As shown in Figure 2, the existence of the sp superdiffraction peak indicates the chemical order of the film. In addition, for this film, we obtained a value of about 16.0 μC / cm in the multiferroic performance test. 2 The polarization intensity.

[0061] Embodiment 4:

[0062] The powders of Bi2O3, Sm2O3, Fe2O3 and Co2O3 with a molar ratio of 1.15:1:1:1 were uniformly mixed to prepare a target material for use; the (001)-Nb-SrTiO3 single crystal substrate was placed on the sample platform of the magnetron sputtering instrument, and the off-axis sputtering angle was adjusted to 33°; the background vacuum was reduced to 1×10 -5 Torr, while maintaining the deposition temperature at 625℃; then Ar and O2 were introduced into the magnetron sputtering chamber to ensure that the Ar / O2 flow ratio was 9:1, the gas flow rate was 10sccm, and the working pressure was 0.4Pa; then 90W RF power was provided to the target material. After deposition for 3.0h, a 120nm thick high-quality Co(BiFe)O4 / BiSmCoFeO6 ordered room temperature multi-iron double perovskite epitaxial composite film was obtained with an order degree of 60%. Its (001) XRD is shown in the attached Figure 4 As shown, there are only diffraction peaks of the spinel second phase, orthorhombic phase ordered film and substrate, indicating the epitaxial nature of the film; with the increase of oxygen / argon ratio, the spinel second phase gradually disappears.

[0063] Embodiment 5:

[0064] The powders of Bi2O3, Sm2O3, Fe2O3 and Co2O3 with a molar ratio of 1.15:1:1:1 were uniformly mixed to prepare a target material for use; the (001)-Nb-SrTiO3 single crystal substrate was placed on the sample platform of the magnetron sputtering instrument, and the off-axis sputtering angle was adjusted to 33°; the background vacuum was reduced to 1×10 -5 Torr, while maintaining the deposition temperature at 625℃; then Ar and O2 were introduced into the magnetron sputtering chamber to ensure that the Ar / O2 flow ratio was 4:6, the gas flow rate was 10sccm, and the working pressure was 0.4Pa; then 90W RF power was provided to the target material. After deposition for 3.0h, a 120nm thick high-quality Co(BiFe)O4 / BiSmCoFeO6 ordered room temperature multi-iron double perovskite epitaxial composite film was obtained with an order degree of 30%. Its (001) XRD is shown in the attached Figure 4 As shown, there are only diffraction peaks of the spinel second phase, orthorhombic phase ordered film and substrate, indicating the epitaxial nature of the film; with the increase of oxygen / argon ratio, the spinel second phase gradually disappears.

[0065] Embodiment 6:

[0066] The powders of Bi2O3, Sm2O3 and Co2O3 with a molar ratio of 1.15:1:2 were uniformly mixed to prepare a target material for use; the (001)-SrTiO3 single crystal substrate was placed on the sample platform of the magnetron sputtering instrument, and the off-axis sputtering angle was adjusted to 33.5°; the background vacuum was reduced to 1×10 -5 Torr, while maintaining the deposition temperature at 575℃; then Ar and O2 were introduced into the magnetron sputtering chamber to ensure that the Ar / O2 flow ratio was 9:1, the gas flow rate was 10sccm, and the working pressure was 0.4Pa; then 90W RF power was provided to the target material, and after deposition for 1.0h, a 28nm thick high-quality Co(BiCo)O4 / BiSmCo2O6 ordered room temperature multi-iron double perovskite epitaxial composite film was obtained with an order degree of 65%. Its (001) XRD is shown in the attached Figure 5 As shown, there are only diffraction peaks of the spinel second phase, orthorhombic phase ordered film and substrate, indicating the epitaxial nature of the film.

[0067] Embodiment 7:

[0068] The powders of Bi2O3, Sm2O3 and Co2O3 with a molar ratio of 1.15:1:2 were uniformly mixed to prepare a target material for use; the (001)-Nb-SrTiO3 single crystal substrate was placed on the sample platform of the magnetron sputtering instrument, and the off-axis sputtering angle was adjusted to 33.5°; the background vacuum was reduced to 1×10 -5 Torr, while maintaining the deposition temperature at 575℃; then Ar and O2 were introduced into the magnetron sputtering chamber to ensure that the Ar / O2 flow ratio was 9:1, the gas flow rate was 10sccm, and the working pressure was 0.4Pa; then 90W RF power was provided to the target material, and after deposition for 1.0h, a 28nm thick high-quality Co(BiCo)O4 / BiSmCo2O6 ordered room temperature multi-iron double perovskite epitaxial composite film was obtained with an order degree of 65%. Its (001) XRD is shown in the attached Figure 5 As shown, there are only diffraction peaks of the spinel second phase, orthorhombic phase ordered film and substrate, indicating the epitaxial nature of the film.

[0069] The above is a detailed introduction to a Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film and preparation process provided in the embodiments of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application; at the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present application.

[0070] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be subject to that defined in the attached claims.

[0071] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0072] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0073] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film, characterized in that: The Bi / Sm-based ordered room temperature multiferroic double perovskite epitaxial composite film is grown on a single crystal substrate, and the molecular structural formula of the Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film is: Co(BiMe)O4 / BiSmCoMeO6.

2. The Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film according to claim 1, characterized in that: The crystal structure of the Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film includes an orthorhombic phase and a second phase, and the space group of the orthorhombic phase is Pbnm, and the order degree is 30%-65%.

3. The Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film according to claim 2, characterized in that: The A-site elements Bi and Sm of the Bi / Sm-based ordered room-temperature multi-iron double perovskite epitaxial composite film have chemical rock salt order, and the chemical rock salt ordered region of Bi and Sm exists at the interface between the orthorhombic phase and the second phase.

4. The Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film according to claim 2, characterized in that: The second phase is a cubic spinel structure, and the chemical formula of the spinel structure is Co(BiMe)O4.

5. The Bi / Sm-based ordered room temperature multi-iron double perovskite epitaxial composite film according to claim 1, characterized in that: The single crystal substrate is SrTiO3 or Nb-SrTiO3.

6. A process for preparing a Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film as claimed in any one of claims 1 to 5, characterized in that: The process comprises the following steps: S1) selecting a single crystal substrate as a substrate, washing it, drying it naturally, and placing it in a sample sputtering platform; S2) prepare a Bi / Sm-based ceramic target and place it in a magnetron sputtering platform. After heating, use radio frequency magnetron sputtering preparation technology to deposit a thin film to obtain a Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film.

7. The process according to claim 6, characterized in that The radio frequency magnetron sputtering preparation technology in S2) is specifically: vacuum is 1-3×10 -5 Torr, the oxygen / argon ratio is 0.1-8:10-2, the sputtering angle is 32.5°-34.0°, the total gas flow rate is 9-11sccm, the working gas pressure is 0.4-0.8Pa, the RF power is 60-120W, and the deposition time is 0.1-4.0 hours.

8. The process according to claim 6, characterized in that The obtained Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film has room temperature ferroelectricity, and the saturated ferroelectric polarization is 15.0-25.0 μC / cm 2 .

9. The process according to claim 7, characterized in that The obtained Bi / Sm-based room temperature multiferroic ordered double perovskite epitaxial composite film has room temperature ferromagnetism, and the saturation magnetization intensity is 9.0-11.0emu / cm 3 .

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