To study the influence of CoFeB/MgO interface on tunneling magnetoresistance （TMR）, different structures of magnetic tunnel junctions （MTJs） are successfully prepared by the magnetron sputtering technique and char...To study the influence of CoFeB/MgO interface on tunneling magnetoresistance （TMR）, different structures of magnetic tunnel junctions （MTJs） are successfully prepared by the magnetron sputtering technique and characterized by atomic force microscopy, a physical property measurement system, x-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that TMR of the CoFeB/Mg/MgO/CoFeB structure is evidently improved in comparison with the CoFeB/MgO/CoFeB structure because the inserted Mg layer prevents Fe-oxide formation at the CoFeB/MgO interface, which occurs in CoFeB/MgO/CoFeB MTJs. The inherent properties of the CoFeB/MgO/CoFeB, CoFeB/Fe-oxide/MgO/CoFeB and CoFeB/Mg/MgO/CoFeB MTJs are simulated by using the theories of density functions and non-equilibrium Green functions. The simulated results demonstrate that TMR of CoFeB/Fe-oxide/MgO/CoFeB MTJs is severely decreased and is only half the value of the CoFeB/Mg/MgO/CoFeB MTJs. Based on the experimental results and theoretical analysis, it is believed that in CoFeB/MgO/CoFeB MTJs, the interface oxidation of the CoFeB layer is the main reason to cause a remarkable reduction of TMR, and the inserted Mg layer may play an important role in protecting Fe atoms from oxidation, and then increasing TMR.展开更多
The dependence of perpendicular magnetic anisotropy （PMA） on the barrier layer MgO thickness in MgO/CoFeB /Ta multilayers is investigated. The results show that the strongest PMA occurs in a small window of about 2 ...The dependence of perpendicular magnetic anisotropy （PMA） on the barrier layer MgO thickness in MgO/CoFeB /Ta multilayers is investigated. The results show that the strongest PMA occurs in a small window of about 2 4nm with the increase of MgO thickness from 1-1Onto. The crystalline degree of MgO and the change of interatomic distance along the out-of-plane direction may be the main reasons for the change of PMA in these multilayers. Moreover, the roughnesses of 2- and 4-nm-thick MgO samples are 3.163 and 1.8 nm, respectively, and both the samples show PMA. These results could be used to tune the magnetic characteristic of the ultra thin CoFeB film for future applications in perpendicular magnetic devices.展开更多
聚焦离子束系统(focus ion beam,FIB)作为一种成熟的材料加工技术,在磁性材料的加工中得到广泛应用。然而,在利用FIB对磁性材料的加工过程中,难免会因为离子的辐照对样品产生影响。本文以CoFeB薄膜为研究对象,研究辐照强度对样品磁性质...聚焦离子束系统(focus ion beam,FIB)作为一种成熟的材料加工技术,在磁性材料的加工中得到广泛应用。然而,在利用FIB对磁性材料的加工过程中,难免会因为离子的辐照对样品产生影响。本文以CoFeB薄膜为研究对象,研究辐照强度对样品磁性质的影响。对于利用离子束辐照来调控薄膜性质具有指导意义。展开更多
An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are relate...An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are related to the CoFeB thickness.When the film is thicker than 3 nm,the side jump mechanism dominates and the weak locaUzation to AHC vanishes.For very thin CoFeB films,both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect,and the weak localization correction to AHC is observed.展开更多
Exchange coupling across the interface between a ferromagnetic(FM)layer and an antiferromagnetic(AFM)or another FM layer may induce a unidirectional magnetic anisotropy and/or a uniaxial magnetic anisotropy,which has ...Exchange coupling across the interface between a ferromagnetic(FM)layer and an antiferromagnetic(AFM)or another FM layer may induce a unidirectional magnetic anisotropy and/or a uniaxial magnetic anisotropy,which has been extensively studied due to the important application in magnetic materials and devices.In this work,we observed a fourfold magnetic anisotropy in amorphous Co Fe B layer when exchange coupling to an adjacent Fe Rh layer which is epitaxially grown on an SrTiO_(3)(001)substrate.As the temperature rises from 300 K to 400 K,Fe Rh film undergoes a phase transition from AFM to FM phase,the induced fourfold magnetic anisotropy in the Co Fe B layer switches the orientation from the Fe Rh<110>to Fe Rh<100>directions and the strength is obviously reduced.In addition,the effective magnetic damping as well as the two-magnon scattering of the Co Fe B/Fe Rh bilayer also remarkably increase with the occurrence of magnetic phase transition of Fe Rh.No exchange bias is observed in the bilayer even when Fe Rh is in the nominal AFM state,which is probably because the residual FM Fe Rh moments located at the interface can well separate the exchange coupling between the below pinned Fe Rh moments and the Co Fe B moments.展开更多
Using in situ electric-field-modulated anisotropic magnetoresistance measurement, a large reversible and non- volatile in-plane rotation of magnetic easy axis of -35° between the positive and negative electrical ...Using in situ electric-field-modulated anisotropic magnetoresistance measurement, a large reversible and non- volatile in-plane rotation of magnetic easy axis of -35° between the positive and negative electrical poling states is demonstrated in C040Fe40B20//（001）-cut Pb（Mgl/3Nb2/3）O3-25PbTiO3 （PMN-PT）. The specific magneto- electric coupling mechanism therein is experimentally verified to be related to the synchronous in-plane strain rotation induced by 109° ferroelastic domain switching in the （001）-cut PMN-PT substrate.展开更多
基金Supported by the National Defense Advance Research Foundation under Grant No 9140A08XXXXXX0DZ106the Basic Research Program of Ministry of Education of China under Grant No JY10000925005+2 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department under Grant No 11JK0912the Scientific Research Foundation of Xi'an University of Science and Technology under Grant No 2010011the Doctoral Research Startup Fund of Xi'an University of Science and Technology under Grant No 2010QDJ029
文摘To study the influence of CoFeB/MgO interface on tunneling magnetoresistance （TMR）, different structures of magnetic tunnel junctions （MTJs） are successfully prepared by the magnetron sputtering technique and characterized by atomic force microscopy, a physical property measurement system, x-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that TMR of the CoFeB/Mg/MgO/CoFeB structure is evidently improved in comparison with the CoFeB/MgO/CoFeB structure because the inserted Mg layer prevents Fe-oxide formation at the CoFeB/MgO interface, which occurs in CoFeB/MgO/CoFeB MTJs. The inherent properties of the CoFeB/MgO/CoFeB, CoFeB/Fe-oxide/MgO/CoFeB and CoFeB/Mg/MgO/CoFeB MTJs are simulated by using the theories of density functions and non-equilibrium Green functions. The simulated results demonstrate that TMR of CoFeB/Fe-oxide/MgO/CoFeB MTJs is severely decreased and is only half the value of the CoFeB/Mg/MgO/CoFeB MTJs. Based on the experimental results and theoretical analysis, it is believed that in CoFeB/MgO/CoFeB MTJs, the interface oxidation of the CoFeB layer is the main reason to cause a remarkable reduction of TMR, and the inserted Mg layer may play an important role in protecting Fe atoms from oxidation, and then increasing TMR.
基金Supported by the National Basic Research Program of China under Grant No 2011CB921804the Beijing Key Subject Foundation of Condensed Matter Physics under Grant No 0114023
文摘The dependence of perpendicular magnetic anisotropy （PMA） on the barrier layer MgO thickness in MgO/CoFeB /Ta multilayers is investigated. The results show that the strongest PMA occurs in a small window of about 2 4nm with the increase of MgO thickness from 1-1Onto. The crystalline degree of MgO and the change of interatomic distance along the out-of-plane direction may be the main reasons for the change of PMA in these multilayers. Moreover, the roughnesses of 2- and 4-nm-thick MgO samples are 3.163 and 1.8 nm, respectively, and both the samples show PMA. These results could be used to tune the magnetic characteristic of the ultra thin CoFeB film for future applications in perpendicular magnetic devices.
文摘聚焦离子束系统(focus ion beam,FIB)作为一种成熟的材料加工技术,在磁性材料的加工中得到广泛应用。然而,在利用FIB对磁性材料的加工过程中,难免会因为离子的辐照对样品产生影响。本文以CoFeB薄膜为研究对象,研究辐照强度对样品磁性质的影响。对于利用离子束辐照来调控薄膜性质具有指导意义。
基金supported by the National Basic Research Program of China(Grant No.2012CB933102)the National Natural Science Foundation of China(Grant Nos.11079052,11174354,and 51172080)
文摘An obvious weak localization correction to anomalous Hall conductance（AHC） in very thin CoFeB film is reported.We find that both the weak localization to AHC and the mechanism of the anomalous Hall effect are related to the CoFeB thickness.When the film is thicker than 3 nm,the side jump mechanism dominates and the weak locaUzation to AHC vanishes.For very thin CoFeB films,both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect,and the weak localization correction to AHC is observed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874150,51871233,and 12174103)the Natural Science Foundation of Shanghai(Grant Nos.21ZR1420500 and 21JC1402300)。
文摘Exchange coupling across the interface between a ferromagnetic(FM)layer and an antiferromagnetic(AFM)or another FM layer may induce a unidirectional magnetic anisotropy and/or a uniaxial magnetic anisotropy,which has been extensively studied due to the important application in magnetic materials and devices.In this work,we observed a fourfold magnetic anisotropy in amorphous Co Fe B layer when exchange coupling to an adjacent Fe Rh layer which is epitaxially grown on an SrTiO_(3)(001)substrate.As the temperature rises from 300 K to 400 K,Fe Rh film undergoes a phase transition from AFM to FM phase,the induced fourfold magnetic anisotropy in the Co Fe B layer switches the orientation from the Fe Rh<110>to Fe Rh<100>directions and the strength is obviously reduced.In addition,the effective magnetic damping as well as the two-magnon scattering of the Co Fe B/Fe Rh bilayer also remarkably increase with the occurrence of magnetic phase transition of Fe Rh.No exchange bias is observed in the bilayer even when Fe Rh is in the nominal AFM state,which is probably because the residual FM Fe Rh moments located at the interface can well separate the exchange coupling between the below pinned Fe Rh moments and the Co Fe B moments.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11374010 and 11434009the Fundamental Research Funds for the Central Universities
文摘Using in situ electric-field-modulated anisotropic magnetoresistance measurement, a large reversible and non- volatile in-plane rotation of magnetic easy axis of -35° between the positive and negative electrical poling states is demonstrated in C040Fe40B20//（001）-cut Pb（Mgl/3Nb2/3）O3-25PbTiO3 （PMN-PT）. The specific magneto- electric coupling mechanism therein is experimentally verified to be related to the synchronous in-plane strain rotation induced by 109° ferroelastic domain switching in the （001）-cut PMN-PT substrate.
