With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead...With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models.In addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.展开更多
Effects of soft-magnetic MnZn ferrite （Mn0.5Zn0.5Fe2O4, MZF） and hard-magnetic Ba ferrite （BaO.6Fe2O3, BaM） on the structure and magnetic transport properties of [La2/3Srl/3MnO3] （LSMO）/（x） [ferrites] （ferrit...Effects of soft-magnetic MnZn ferrite （Mn0.5Zn0.5Fe2O4, MZF） and hard-magnetic Ba ferrite （BaO.6Fe2O3, BaM） on the structure and magnetic transport properties of [La2/3Srl/3MnO3] （LSMO）/（x） [ferrites] （ferrites=MZF, BaM） composites have been investigated. It was found that the inclusion of MZF phase reduces magnetization and ferromagnetic-paramagnetic transition temperature （To） of the composites. With increasing the content of the dopants, the high-temperature magnetoresistance （MR） decreases, whereas low-temperature MR increases and reaches 42% at 150 K and x=0.1. However, for the LSMO/BaM composites, magnetization and ferromagneticparamagnetic transition temperature （To） decrease firstly as x〈5%, and then increase as x〉5%. The resistivity of the composites increases by five orders of magnitude at x=1% and is out of measured range at x=5%. High magnetic field has little effect on the resistivity and magnetoresistance originate from the pinning effect of BaM for the composites with x〉5%, which may grains.展开更多
We combine effective medium theory(EMT) with the two-channel conducting model to study the magnetic granular concentration dependence of a giant magnetoresistance(GMR) in magnetic granular composites.The composite is ...We combine effective medium theory(EMT) with the two-channel conducting model to study the magnetic granular concentration dependence of a giant magnetoresistance(GMR) in magnetic granular composites.The composite is composed of small magnetic granules (such as Co) embedded in an immiscible nonmagnetic metallic matrix (such as Ag).We consider the influence of granule size and concentration respectively.Firstly,granules have a distribution in size,resulting in superparamagnetic(SPM) granules and ferromagnetic granules which have different contributions to conductance.Secondly,the effective surface scattering is changed with the changes of concentration.The calculated result of GMR is in agreement with theexperimental data.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 51125004,10974120,B13029 and JQ200901)the National Basic Research Program of China (Grant Nos. 2013CB922303and 2009CB929202)
文摘With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models.In addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.
文摘Effects of soft-magnetic MnZn ferrite （Mn0.5Zn0.5Fe2O4, MZF） and hard-magnetic Ba ferrite （BaO.6Fe2O3, BaM） on the structure and magnetic transport properties of [La2/3Srl/3MnO3] （LSMO）/（x） [ferrites] （ferrites=MZF, BaM） composites have been investigated. It was found that the inclusion of MZF phase reduces magnetization and ferromagnetic-paramagnetic transition temperature （To） of the composites. With increasing the content of the dopants, the high-temperature magnetoresistance （MR） decreases, whereas low-temperature MR increases and reaches 42% at 150 K and x=0.1. However, for the LSMO/BaM composites, magnetization and ferromagneticparamagnetic transition temperature （To） decrease firstly as x〈5%, and then increase as x〉5%. The resistivity of the composites increases by five orders of magnitude at x=1% and is out of measured range at x=5%. High magnetic field has little effect on the resistivity and magnetoresistance originate from the pinning effect of BaM for the composites with x〉5%, which may grains.
文摘We combine effective medium theory(EMT) with the two-channel conducting model to study the magnetic granular concentration dependence of a giant magnetoresistance(GMR) in magnetic granular composites.The composite is composed of small magnetic granules (such as Co) embedded in an immiscible nonmagnetic metallic matrix (such as Ag).We consider the influence of granule size and concentration respectively.Firstly,granules have a distribution in size,resulting in superparamagnetic(SPM) granules and ferromagnetic granules which have different contributions to conductance.Secondly,the effective surface scattering is changed with the changes of concentration.The calculated result of GMR is in agreement with theexperimental data.
