The magneto-optical Kerr effect susceptometry technique is proposed to determine the uniaxial magnetic anisotropy （UMA） constant Ku. The magnetic properties of Cu/Fe/SiO2/Si grown by dc magnetron sputtering were investigated. The in-plane uniaxial magnetic anisotropy was probed by the magneto-optical Kerr effect （MOKE）. The value of UMA, Ku = 2.5 x 103 J/m3, was simulated from the field dependence of ac susceptibility along the hard axis according to the Stoner-Wohlfarth （S-W） model, which is consistent with Ku = 2.7~ 103 J/m3 calculated from the magnetic hysteresis loops. Our results show that the magneto-optical Kerr effect susceptometry can be employed to determine the magnetic anisotropy constant owing to its high sensitivity.
The Jahn-Teller distortion plays an important role in determining the exchange interaction in rare-earth manganites.In this work we study the influence of the Jahn-Teller distortion on the magnetic structures of TbMn1-xFexO3（x = 0,0.02,0.05,0.10,and 0.20） single crystals in the basal MnO2 plane.The decrease in the quadruple splitting with the increasing Fe doping indicates the reduction of the Jahn-Teller distortion,which makes the nearest neighboring（NN） FM interaction dominant over the next nearest neighbor（NNN） AFM interaction.This alteration is favorable for the development of A-type AFM ordering instead of the spiral magnetic ordering,which collapses when x ≥ 0.05.The analysis of dielectric data indicates that the ferroelectricity is arising from the peculiar spiral magnetic ordering.
本文利用高温油相法制备出尺寸、形状均一的MnO纳米颗粒,X射线衍射图(XRD)和透射电子显微镜(TEM)照片清晰表明MnO纳米颗粒为单一的面心立方岩盐晶体结构,尺寸为15 nm,粒径分布很窄.通过零场冷却(ZFC)和带场冷却(FC)的磁滞回线发现MnO纳米颗粒具有明显的交换偏置效应,而且磁滞回线同时表现出横向和纵向偏移.横向偏移说明纳米颗粒中两相复合的存在,纵向偏移说明了存在自旋玻璃相或者超顺磁相.进而通过不同频率下随温度变化的交流磁化率的测定,根据Mydosh的经验数值确认MnO纳米颗粒表面层为自旋玻璃相,并得到MnO纳米颗粒表面自旋玻璃相的转变温度为TSG=32 K.
According to density functional theory （DFT） using the plane wave base and pseudo-potential, we investigate the effects of the specific location of oxygen vacancy （Vo） in a （Ti,Co）06 distorted octahedron on the spin density and magnetic properties of Co-doped rutile Ti02 dilute magnetic semiconductors. Our calculations suggest that the Vo location has a significant influence on the magnetic moment of individual Co cations. In the case where two Co atoms are separated far away from each other, when the Vo is located at the equatorial site of a Co-contained octahedron, the ground state of the two Co cations is d6（t3g↑, t23g ↓） without any magnetic moment. However, if the Vo is located at the apical site, these two Co sites have different ground states and magnetic moments. The spin densities are also observed to be modified by the exchange coupling between the Co cations and the location of Vo. Some positive spin polarization is induced around the adjacent O ions.
