CN110228822A - A kind of Ferromagnetic/Antiferromagnetic hetero-junctions and its preparation with exchange bias effect - Google Patents

A kind of Ferromagnetic/Antiferromagnetic hetero-junctions and its preparation with exchange bias effect Download PDF

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CN110228822A
CN110228822A CN201910415278.8A CN201910415278A CN110228822A CN 110228822 A CN110228822 A CN 110228822A CN 201910415278 A CN201910415278 A CN 201910415278A CN 110228822 A CN110228822 A CN 110228822A
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bifeo
mfe
junctions
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dry film
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傅邱云
仲世豪
王超宏
周令
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Huazhong University of Science and Technology
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Abstract

The invention belongs to field of magnetic material, more particularly, to a kind of Ferromagnetic/Antiferromagnetic hetero-junctions with exchange bias effect and its preparation.More iron hetero-junctions have MFe2O4/BiFeO3Double membrane structure, wherein MFe2O4As ferromagnetic layer, BiFeO3As inverse ferric magnetosphere, M is Ni or Co.Select the inverse spinel type ferrite MFe with high-curie temperature2O4(M=Co, Ni) is used as ferromagnetic material, makes full use of MFe2O4Curie temperature and BiFeO3Ne&1&el temperature it is close, in room temperature with excellent ferromagnetism, the very high potential with raising system cut-off temperature.More iron hetero-junctions provided by the invention, CoFe2O4The coercive field H of/BiFeO3 bilayer filmC=15.84KOe, and apparent exchange bias field (H has also been observed in 3KEB(3K)=- 142.5Oe).

Description

A kind of Ferromagnetic/Antiferromagnetic hetero-junctions and its preparation with exchange bias effect
Technical field
The invention belongs to field of magnetic material, more particularly, to a kind of Ferromagnetic/Antiferromagnetic with exchange bias effect Hetero-junctions and its preparation, more particularly, to a kind of at room temperature with the Ferromagnetic/Antiferromagnetic hetero-junctions and its system of exchange bias effect It is standby.
Background technique
Multi-ferroic material is considered as grinding due to having the multiple performances such as ferroelectricity, ferromagnetism and magnetoelectric effect simultaneously Study carefully one of novel memory devices part and the most potential candidate material of logical device.But it is tired due to material preparation and microscopic sdIBM-2+2q.p.approach Difficulty, research is slow always.Until 2003, the researchers such as Wang of University of California report on Science, using sharp Light pulse deposition method (PLD), epitaxial growth more iron BiFeO3 films of tetragonal crystal system, spontaneous pole on SrTiO3 substrate Change intensity and reached 63.2 μ C/cm2, and observes that there are apparent magnetoelectric effects in the material.This discovery allows people See the practical dawn of multi-iron material.
Exchange bias effect refers to that Ferromagnetic/Antiferromagnetic system is cold from the Ne&1&el temperature for being higher than antiferromagnet in external magnetic field When but arriving low temperature, the hysteresis loop of ferromagnetic layer material along magnetic field axle offset origin, while with coercivity increase the phenomenon that.From Since discovery based on exchange biased Spin Valve (SpinValve) effect in 1991, the magnetic electronic based on exchange bias effect Device is widely applied to magnetic reading head, in magnetic random memory and resistive formula memory, becomes the area research Hot spot.Based on multi-iron material and exchange bias effect, in the antiferromagnetic Cr of Borisov in 2005 et al. magnetoelectricity2O3(111) single The multilayer film that brilliant and Co/Pt is formed is realized with the exchange biased of cooling direction of an electric field change, they are it is thought that because Cr2O3 Spin configuration of antiferromagnet change interface Net magnetic moment can be caused to change, but this is not isothermal electric field tune truly It controls exchange biased.Chu of University of California Berkeley et al. is in BiFeO3It is realized and is played a game by electric field in/CoFe hetero-junctions The reversible control of domain magnetism, but the whole magnetic reversible control that can't be observed by macroscopical hysteresis loop.
Chinese patent literature CN104362250A discloses a kind of La0.7Sr0.3MnO3As ferromagnetic layer and bottom electrode layer, mix It is miscellaneous to have one of Ba, Ca, Sr, Pb or a variety of BiFeO3As more iron hetero-junctions of inverse ferric magnetosphere preparation, have stronger Exchange bias effect, but the pulse laser deposition process higher cost used do not meet industrialization needs.
Chinese patent literature CN104313685A discloses one kind using ferrous oxide as inverse ferric magnetosphere, and ferroso-ferric oxide is Magnetospheric more iron hetero-junctions, are successfully prepared the oxide ferroelectric thin film with exchange bias effect, but do not have at room temperature Exchange bias effect.
There is strong exchange biased condition, the Curie temperature T of ferromagnetic phase from FM/AFMCAntiferromagnetic phase need to be greater than how You are temperature TN。La1-xAxMnO3The Curie temperature of material system is difficult only in 300K or so by BiFeO3/La1-xAxMnO3Hetero-junctions Cut-off temperature be increased to room temperature or more.And La1-xAxMnO3The Curie temperature of material system is also far below BiFeO3Nai Er Temperature does not make full use of BiFeO3The advantage of high Ne&1&el temperature.
Summary of the invention
Aiming at the above defects or improvement requirements of the prior art, the present invention provides a kind of iron with exchange bias effect Magnetic/antiferromagnetic hetero-junctions and its preparation, its object is to by with BiFeO3As inverse ferric magnetosphere, CoFe2O4As ferromagnetic layer, A kind of Ferromagnetic/Antiferromagnetic hetero-junctions is proposed, the more iron hetero-junctions for thus solving the prior art do not have exchange partially at room temperature The technical issues of setting effect.
To achieve the above object, according to one aspect of the present invention, provide it is a kind of with exchange bias effect it is ferromagnetic/ Antiferromagnetic hetero-junctions, with MFe2O4/BiFeO3Double membrane structure, wherein MFe2O4As ferromagnetic layer, BiFeO3As anti-iron Magnetosphere, M are Ni or Co；The MFe2O4/BiFeO3Double membrane structure makes the hetero-junctions have exchange bias effect.
Preferably, the ferromagnetic layer with a thickness of 200nm-300nm, the inverse ferric magnetosphere with a thickness of 50nm-60nm.
Preferably, the double membrane structure is located on substrate, and the substrate is SrTiO3, Si or Si/SiO2。
Preferably, the substrate with a thickness of 0.5mm-1mm.
Preferably, the hetero-junctions has exchange bias effect at 300k, and exchange bias magnetic field is -3.5Oe.
Other side according to the invention provides the preparation method of hetero-junctions described in one kind, includes the following steps:
(1) by BiFeO3Precursor solution is coated in substrate surface, dries after film forming, repeats the coating and the drying The step of it is multiple, obtain BiFeO3Dry film；The wherein BiFeO3BiFeO in precursor solution3Concentration be 0.15mol/L- 0.2mol/L；
(2) by MFe2O4Precursor solution is coated in the BiFeO3Dry film surface is dried after film forming, is obtained from bottom to top It is sequentially located at the BiFeO of substrate surface3Dry film and MFe2O4Dry film, wherein MFe2O4MFe in precursor solution2O4Concentration be 0.15mol/L-0.2mol/L, M are Ni or Co；
(3) by the BiFeO positioned at substrate surface3Dry film and MFe2O4Dry film is made annealing treatment, and is obtained described heterogeneous Knot.
Preferably, the BiFeO3Precursor solution obtains by the following method: according to BiFeO3Stoichiometric ratio, by nitre Sour iron and bismuth nitrate are dissolved in ethylene glycol monomethyl ether, obtain that the lemon with amounts of substances such as ferro elements is added in the backward solution of solution Lemon acid, stirs to get the BiFeO3Precursor solution.
Preferably, the MFe2O4Precursor solution obtains by the following method: according to MFe2O4Stoichiometric ratio, by nitre Sour iron and cobalt nitrate or ferric nitrate and nickel nitrate, are dissolved in ethylene glycol monomethyl ether, obtain being added in the backward solution of solution with The citric acid of the amount of the substances such as ferro element stirs to get the MFe2O4Precursor solution.
Preferably, the drying carries out at 200~250 DEG C.
Preferably, the annealing temperature is 600-700 DEG C, and annealing time is 2-3 hours.
In general, through the invention it is contemplated above technical scheme is compared with the prior art, can obtain down and show Beneficial effect:
(1) the present invention provides a kind of at room temperature with the Ferromagnetic/Antiferromagnetic hetero-junctions of exchange bias effect, has MFe2O4/BiFeO3Double membrane structure, wherein MFe2O4As ferromagnetic layer, BiFeO3As inverse ferric magnetosphere, M is Ni or Co；This hair Bright selection has the inverse spinel type ferrite MFe of high-curie temperature2O4(M=Co, Ni) is used as ferromagnetic material, makes full use of MFe2O4Curie temperature and BiFeO3Ne&1&el temperature it is close, in room temperature with excellent ferromagnetism, there is raising system to cut The only very high potential of temperature.
(2) more iron hetero-junctions provided by the invention, CoFe2O4The coercive field H of/BiFeO3 bilayer filmC=15.84KOe, And apparent exchange bias field (H has also been observed in 3KEB(3K)=- 142.5Oe).In addition the hetero-junctions has friendship at 300k Bias effect is changed, exchange bias magnetic field is -3.5Oe, and cut-off temperature has reached room temperature.
(3) present invention is mainly prepared for MFe using sol-gal process and spin-coating method on substrate2O4/BiFeO3Hetero-junctions, Preparation method is simple.
Detailed description of the invention
Fig. 1 is the MFe that the embodiment of the present invention 1 is prepared2O4/BiFeO3The structural schematic diagram of film；
Fig. 2 is BiFeO in duplicature heterojunction structure that the embodiment of the present invention 1 is prepared3Film XRD diagram.
BiFeO in the duplicature heterojunction structure that Fig. 3 embodiment of the present invention 1 is prepared3Film SEM figure；
Fig. 4 is CoFe in duplicature heterojunction structure that the embodiment of the present invention 1 is prepared2O4Film XRD diagram.
CoFe in the duplicature heterojunction structure that Fig. 5 embodiment of the present invention 1 is prepared2O4Film SEM figure；
Fig. 6 is CoFe2O4The M-H hysteresis loop figure of film at different temperatures；
Fig. 7 is the duplicature hetero-junctions CoFe that the embodiment of the present invention 1 is prepared2O4/BiFeO3Bilayer film is in not equality of temperature M-H hysteresis loop figure under degree.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and It is not used in the restriction present invention.As long as in addition, technical characteristic involved in the various embodiments of the present invention described below Not constituting a conflict with each other can be combined with each other.
The present invention provides a kind of Ferromagnetic/Antiferromagnetic hetero-junctions with exchange bias effect, with MFe2O4/ BiFeO3Double membrane structure, wherein MFe2O4As ferromagnetic layer, BiFeO3As inverse ferric magnetosphere, M is Ni or Co；The MFe2O4/ BiFeO3Double membrane structure makes the hetero-junctions have exchange bias effect.
In some embodiments, the ferromagnetic layer with a thickness of 50-60nm, the inverse ferric magnetosphere with a thickness of 200nm- 300nm。
In some embodiments, the double membrane structure is located on substrate, and the substrate is SrTiO3, Si or Si/SiO2.Its Middle Si/SiO2Indicate the composite layer of silicon and silica.
In some embodiments, the substrate with a thickness of 0.5mm or 1mm.
More iron hetero-junctions that the present invention improves, wherein CoFe2O4The coercive field H of/BiFeO3 bilayer filmC=15.84KOe, The hetero-junctions has exchange bias effect at 300k, and exchange bias magnetic field is -3.5Oe, and cut-off temperature has reached room temperature.This hair The bright room temperature broadly can refer to 20-30 DEG C, also can refer to 300K in the narrow sense.
The present invention is using sol-gal process and spin-coating method in SrTiO3CoFe is prepared on substrate2O4/BiFeO3Hetero-junctions. Specific preparation method and steps are as follows:
A. solution is prepared: configuration BiFeO3Precursor solution and MFe2O4Precursor solution is stand-by；
B. it cleans substrate: substrate being placed in different organic solution, be cleaned by ultrasonic；
C. spin coating wet film: by the method for spin coating, precursor solution is thrown away film forming；
D. wet film is dried: being dried using heating plate, wet film dry out solvent is made to become dry film；
E. step c is repeated, several times, spin coating several layers are finally intact dry film to d；
F. it anneals: the dry film prepared being annealed in chamber type electric resistance furnace, naturally cools to room temperature；
G. exchange bias effect: PPMS test macro is utilized, tests temperature to CoFe2O4/BiFeO3, hetero-junctions exchange The influence of bias effect.
The preparation method of hetero-junctions described in one kind provided by the invention, includes the following steps:
(1) by BiFeO3Precursor solution is coated in substrate surface, dries after film forming, repeats the coating and the drying The step of it is multiple, obtain BiFeO3Dry film；The wherein BiFeO3BiFeO in precursor solution3Concentration be 0.15mol/L- 0.2mol/L；
(2) by MFe2O4Precursor solution is coated in the BiFeO3Dry film surface is dried after film forming, is obtained from bottom to top It is sequentially located at the BiFeO of substrate surface3Dry film and MFe2O4Dry film, wherein MFe2O4MFe in precursor solution2O4Concentration be 0.15mol/L-0.2mol/L, M are Ni or Co；
(3) by the BiFeO positioned at substrate surface3Dry film and MFe2O4Dry film is made annealing treatment, and is obtained described heterogeneous Knot.
In some embodiments, the BiFeO3Precursor solution obtains by the following method: according to BiFeO3Stoichiometry Than ferric nitrate and bismuth nitrate being dissolved in ethylene glycol monomethyl ether, wherein due to BiFeO3In Bi element it is volatile, so need Bismuth is excessive, obtains that the citric acid with amounts of substances such as ferro elements is added in the backward solution of solution, and reaction generates colloidal sol, finally plus Enter ethylene glycol monomethyl ether constant volume, stirs to get the BiFeO3Precursor solution.
In some embodiments, the MFe2O4Precursor solution obtains by the following method: according to MFe2O4Stoichiometry Than being dissolved in ferric nitrate and cobalt nitrate or ferric nitrate and nickel nitrate in ethylene glycol monomethyl ether, obtaining the backward solution of solution The citric acid of the amount of substances such as middle addition and ferro element, reaction generate colloidal sol, are eventually adding ethylene glycol monomethyl ether constant volume, stir to get The MFe2O4Precursor solution.
It in some embodiments, is coated by the way of spin coating, using sol evenning machine spin-coating film, the revolving speed of sol evenning machine is set It is set to low speed 600-800 and turns/min, time 6-9s；High speed 3000-6000 turns/min, time 25-30s.First low speed spin coating spin coating, High speed spin coating rejection film afterwards.
In some embodiments, solvent is first filled into substrate before spin coating, carries out spin coating operation again after standing 10-20s, in this way at Film quality is higher.
In some embodiments, step (1) prepares BiFeO3When dry film, the step 5-7 of the coating and the drying is repeated It is secondary, to obtain the BiFeO of suitable thickness3Dry film；And step (2) prepares MFe2O4When dry film, only coating is primary, for reality Exchange bias effect on existing heterojunction boundary, ferromagnetic layer should do thin as far as possible.
In some embodiments, the drying carries out at 200~250 DEG C.
In some embodiments, the annealing temperature is 600-700 DEG C, and annealing time is 2-3 hours.
Present invention selection has the inverse spinel type ferrite MFe of high-curie temperature2O4(M=Co, Ni) is used as ferromagnetic material Material, MFe2O4Curie temperature and BiFeO3Ne&1&el temperature it is close, in room temperature with excellent ferromagnetism, have and improve body It is the very high potential of cut-off temperature.
The following are embodiments:
Embodiment 1
First configuration concentration be 0.2mol/L BiFeO3Precursor solution determines colloidal sol object according to the volume of configuration colloidal sol The amount of matter, due to BiFeO3In Bi element it is volatile, therefore excessive Bi element need to be configured.Weigh appropriate ferric nitrate and nitric acid Bismuth, by weighed bismuth nitrate, ferric nitrate is dissolved in suitable ethylene glycol monomethyl ether, is ceaselessly stirred, is obtained with magnetic stir bar The solution uniform to clarification.Into the above solution, the citric acid of the amount of substances such as addition, reaction generate colloidal sol, are eventually adding second two Alcohol methyl ether constant volume, with magnetic stirrer 3h or so, until stirring evenly solution for later use.Before spin coating, respectively use toluene, acetone, With washes of absolute alcohol SrTiO3Substrate, drying are stand-by.Then by configured solution sol evenning machine spin-coating film, sol evenning machine The slow-speed of revolution is set as 800 turns/min, time 9s, and high revolving speed is set as 3000 turns/min, time 25s.After spin-coating film, 200~250 DEG C of heating plate drying, make dry film.It repeats above spin coating baking step 6 times, the preparation of dry film can be completed. It is stand-by that in 2h that dry film is annealed in 650 DEG C of air inverse ferric magnetosphere film is prepared in dry film.
It is reconfigured the CoFe that concentration is 0.2mol/L2O4Precursor solution determines collosol substance according to the volume of configuration colloidal sol Amount, weigh suitable ferric nitrate and cobalt nitrate, by weighed cobalt nitrate, ferric nitrate is dissolved in suitable ethylene glycol monomethyl ether In, it is ceaselessly stirred with magnetic stir bar, obtains clarifying uniform solution.The lemon of the amount of substances such as addition into the above solution Acid, reaction generates colloidal sol, is eventually adding ethylene glycol monomethyl ether constant volume, with magnetic stirrer 3h or so, until stirring evenly solution For use, in the BiFeO of previous step preparation3Spin coating is carried out on film, the slow-speed of revolution of sol evenning machine is set as 800 turns/min, and the time is 9s, high revolving speed are set as 6000 turns/min, time 25s.It one layer of spin coating, after spin-coating film, is heated at 200~250 DEG C Plate drying, makes dry film.Inverse ferric magnetosphere is prepared in 2h that dry film is annealed in 650 DEG C of air in dry film afterwards BiFeO3/ ferromagnetic layer CoFe2O4More iron hetero-junctions.
The more iron heterojunction structure schematic diagrames of the inverse ferric magnetosphere/ferromagnetic layer being prepared as shown in Figure 1, be respectively from bottom to top SrTiO3Substrate layer, BiFeO3Layer and MFe2O4Layer, MFe in the embodiment2O4Layer is CoFe2O4Layer.Wherein SrTiO3Substrate thickness For 0.5mm, CoFe2O4Layer is with a thickness of 50nm, BiFeO3Layer is with a thickness of 215nm.
The BiFeO being prepared3Its XRD diagram of dry film is as shown in Figure 2, it can be seen that it is pure BiFeO3Phase.BiFeO3Dry film SEM figure is as shown in Figure 3, it can be seen that crystallite dimension is about 65-100nm, and film particles are fine and closely woven and growth is uniform, film surface light Cunning, fine and close and gap are less.
The CoFe being prepared2O4Its XRD diagram of dry film is as shown in Figure 4, it can be seen that it is pure CoFe2O4Phase.CoFe2O4It is dry Film SEM figure is as shown in Figure 5, it will thus be seen that crystallite dimension is about 55-75nm, and the sky of large area does not occur in compact crystallization Gap, film surface are flat and smooth.
The CoFe that will be prepared2O4/BiFeO3Duplicature carries out PPMS test, and the CoFe with single layer2O4Film carries out Compare, Fig. 6 CoFe2O4The M-H hysteresis loop of film at different temperatures, Fig. 7 CoFe2O4/BiFeO3Duplicature is in difference At a temperature of M-H hysteresis loop.As can be seen that as the temperature rises, the CoFe that the present embodiment is prepared2O4/BiFeO3It is double Saturation magnetization (the M of tunicS), saturation magnetic field (Hs), exchange bias magnetic field (HEB) and coercive field (HC) reduce, CoFe2O4/BiFeO3Hetero-junctions also observed exchange bias field (H at room temperatureEB(300K)=- 3.5Oe), CoFe2O4/ BiFeO3The cut-off temperature of hetero-junctions is apparently higher than the La of the prior art1-xAxMnO3/BiFeO3System.
Embodiment 2
First configuration concentration be 0.15mol/L BiFeO3Precursor solution determines colloidal sol according to the volume of configuration colloidal sol The amount of substance, due to BiFeO3In Bi element it is volatile, therefore excessive Bi element need to be configured.Weigh appropriate ferric nitrate and nitric acid Bismuth, by weighed bismuth nitrate, ferric nitrate is dissolved in suitable ethylene glycol monomethyl ether, is ceaselessly stirred, is obtained with magnetic stir bar The solution uniform to clarification.Into the above solution, the citric acid of the amount of substances such as addition, reaction generate colloidal sol, are eventually adding second two Alcohol methyl ether constant volume, with magnetic stirrer 3h or so, until stirring evenly solution for later use.Before spin coating, respectively use toluene, acetone, With washes of absolute alcohol SrTiO3Substrate, drying are stand-by.Then by configured solution sol evenning machine spin-coating film, sol evenning machine The slow-speed of revolution is set as 800 turns/min, time 9s, and high revolving speed is set as 3000 turns/min, time 25s.After spin-coating film, 200~250 DEG C of heating plate drying, make dry film.It repeats above spin coating baking step 6 times, the preparation of dry film can be completed. It is stand-by that in 2h that dry film is annealed in 650 DEG C of air inverse ferric magnetosphere film is prepared in dry film.
It is reconfigured the CoFe that concentration is 0.15mol/L2O4Precursor solution determines colloidal sol object according to the volume of configuration colloidal sol The amount of matter weighs suitable ferric nitrate and cobalt nitrate, and by weighed cobalt nitrate, ferric nitrate is dissolved in suitable ethylene glycol monomethyl ether In, it is ceaselessly stirred with magnetic stir bar, obtains clarifying uniform solution.The lemon of the amount of substances such as addition into the above solution Acid, reaction generates colloidal sol, is eventually adding ethylene glycol monomethyl ether constant volume, with magnetic stirrer 3h or so, until stirring evenly solution For use, in the BiFeO of previous step preparation3Spin coating is carried out on film, the slow-speed of revolution of sol evenning machine is set as 800 turns/min, and the time is 9s, high revolving speed are set as 6000 turns/min, time 25s.It one layer of spin coating, after spin-coating film, is heated at 200~250 DEG C Plate drying, makes dry film.Inverse ferric magnetosphere is prepared in 2h that dry film is annealed in 700 DEG C of air in dry film afterwards BiFeO3/ ferromagnetic layer CoFe2O4More iron hetero-junctions.
Embodiment 3
First configuration concentration be 0.2mol/L BiFeO3Precursor solution determines colloidal sol object according to the volume of configuration colloidal sol The amount of matter, due to BiFeO3In Bi element it is volatile, therefore excessive Bi element need to be configured.Weigh appropriate ferric nitrate and nitric acid Bismuth, by weighed bismuth nitrate, ferric nitrate is dissolved in suitable ethylene glycol monomethyl ether, is ceaselessly stirred, is obtained with magnetic stir bar The solution uniform to clarification.Into the above solution, the citric acid of the amount of substances such as addition, reaction generate colloidal sol, are eventually adding second two Alcohol methyl ether constant volume, with magnetic stirrer 3h or so, until stirring evenly solution for later use.Before spin coating, respectively use toluene, acetone, With washes of absolute alcohol SrTiO3Substrate, drying are stand-by.Then by configured solution sol evenning machine spin-coating film, sol evenning machine The slow-speed of revolution is set as 800 turns/min, time 9s, and high revolving speed is set as 3000 turns/min, time 25s.After spin-coating film, 200~250 DEG C of heating plate drying, make dry film.It repeats above spin coating baking step 6 times, the preparation of dry film can be completed. It is stand-by that in 2h that dry film is annealed in 650 DEG C of air inverse ferric magnetosphere film is prepared in dry film.
It is reconfigured the NiFe that concentration is 0.2mol/L2O4Precursor solution determines collosol substance according to the volume of configuration colloidal sol Amount, weigh suitable ferric nitrate and nickel nitrate, by weighed nickel nitrate, ferric nitrate is dissolved in suitable ethylene glycol monomethyl ether In, it is ceaselessly stirred with magnetic stir bar, obtains clarifying uniform solution.The lemon of the amount of substances such as addition into the above solution Acid, reaction generates colloidal sol, is eventually adding ethylene glycol monomethyl ether constant volume, with magnetic stirrer 3h or so, until stirring evenly solution For use, in the BiFeO of previous step preparation3Spin coating is carried out on film, the slow-speed of revolution of sol evenning machine is set as 800 turns/min, and the time is 9s, high revolving speed are set as 6000 turns/min, time 25s.It one layer of spin coating, after spin-coating film, is heated at 200~250 DEG C Plate drying, makes dry film.Inverse ferric magnetosphere is prepared in 3h that dry film is annealed in 650 DEG C of air in dry film afterwards BiFeO3/ ferromagnetic layer NiFe2O4More iron hetero-junctions.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to The limitation present invention, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should all include Within protection scope of the present invention.

Claims (10)

1. a kind of Ferromagnetic/Antiferromagnetic hetero-junctions with exchange bias effect, which is characterized in that it is with MFe2O4/BiFeO3It is double Film structure, wherein MFe2O4As ferromagnetic layer, BiFeO3As inverse ferric magnetosphere, M is Ni or Co；The MFe2O4/BiFeO3It is double Film structure makes the hetero-junctions have exchange bias effect.
2. hetero-junctions as described in claim 1, which is characterized in that the ferromagnetic layer with a thickness of 200nm-300nm, it is described anti- Ferromagnetic layer with a thickness of 50nm-60nm.
3. hetero-junctions as claimed in claim 1 or 2, which is characterized in that the double membrane structure is located on substrate, the substrate For SrTiO3, Si or Si/SiO2。
4. hetero-junctions as claimed in claim 3, which is characterized in that the substrate with a thickness of 0.5mm-1mm.
5. hetero-junctions as described in claim 1, which is characterized in that the hetero-junctions has exchange bias effect at 300k, hands over Changing bias magnetic field is -3.5Oe.
6. such as the preparation method of hetero-junctions described in any one of claim 1 to 5, which comprises the steps of:
(1) by BiFeO3Precursor solution is coated in substrate surface, dries after film forming, repeats the step of the coating and the drying It is rapid multiple, obtain BiFeO3Dry film；The wherein BiFeO3BiFeO in precursor solution3Concentration be 0.15mol/L- 0.2mol/L；
(2) by MFe2O4Precursor solution is coated in the BiFeO3Dry film surface is dried after film forming, is obtained from bottom to top successively Positioned at the BiFeO of substrate surface3Dry film and MFe2O4Dry film, wherein MFe2O4MFe in precursor solution2O4Concentration be 0.15mol/L-0.2mol/L, M are Ni or Co；
(3) by the BiFeO positioned at substrate surface3Dry film and MFe2O4Dry film is made annealing treatment, and the hetero-junctions is obtained.
7. preparation method as claimed in claim 6, which is characterized in that the BiFeO3Precursor solution obtains by the following method : according to BiFeO3Ferric nitrate and bismuth nitrate are dissolved in ethylene glycol monomethyl ether by stoichiometric ratio, obtain the backward solution of solution The citric acid of the amount of substances such as middle addition and ferro element, stirs to get the BiFeO3Precursor solution.
8. preparation method as claimed in claim 6, which is characterized in that the MFe2O4Precursor solution obtains by the following method : according to MFe2O4Ferric nitrate and cobalt nitrate or ferric nitrate and nickel nitrate are dissolved in ethylene glycol monomethyl ether by stoichiometric ratio In, it obtains that the citric acid with amounts of substances such as ferro elements is added in the backward solution of solution, stirs to get the MFe2O4Presoma Solution.
9. preparation method as claimed in claim 6, which is characterized in that the drying carries out at 200~250 DEG C.
10. preparation method as claimed in claim 6, which is characterized in that the annealing temperature is 600-700 DEG C, annealing time It is 2-3 hours.
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