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1.
The magnetic and electrical properties of nonmagnetic Ga +3 ion substitution for Mn site are investigated in the bilayer manganite La 1.2 Sr 1.8 Mn 2 O 7.When the Mn is substituted by Ga,the ferromagnetic property obviously weakens,the magnetic transition temperature decreases and a spin-glass behaviour occurs at low temperature.Meanwhile,doping causes the resistivity to dramatically increase,the metal-insulator transition temperature to disappear,and a greater magneto-resistance effect to occur at low temperature.These effects result from the fact that Ga substitution dilutes the magnetic active Mn-O-Mn network and weakens the double exchange interaction,and further suppresses ferromagnetic ordering and metallic conduction. 相似文献
2.
Effects of oxygen vacancy location on the electronic structure and spin density of Co-doped rutile TiO2 dilute magnetic semiconductors 下载免费PDF全文
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. 相似文献
3.
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. 相似文献
4.
Effects of oxygen vacancy location on the electronic structure and spin density of Co-doped rutile TiO<sub>2</sub> dilute magnetic semiconductors 下载免费PDF全文
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)O 6 distorted octahedron on the spin density and magnetic properties of Co-doped rutile TiO2 dilute magnetic semiconductors. Our calculations suggest that the V O 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 V O is located at the equatorial site of a Co-contained octahedron, the ground state of the two Co cations is d6 (t3 2g ↑, t 3 2g ↓) without any magnetic moment. However, if the V O 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 V O . Some positive spin polarization is induced around the adjacent O ions. 相似文献
5.
Determination of the magnetic anisotropy constant of Cu/Fe/SiO2/Si by a magneto-optical Kerr effect susceptometer 下载免费PDF全文
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= 2.5×103J/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= 2.7×103J/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. 相似文献
6.
STRUCTURE, MAGNETIC PROPERTIES AND GIANT MAGNETORESISTANCE OF YMn6Sn6-xGax (x=0-0.6) COMPOUNDS 下载免费PDF全文
Structure, magnetic and transport properties of YMn6Sn6-xGax (0≤x≤0.6) compounds with a HfFe6Ge6-type structure were investigated. It was found that the Ga substitution leads to a contraction of the unit-cell volume. A transition from an antiferromagnetic to a ferromagnetic (or ferrimagnetic) state can be observed for samples (0.1≤x≤0.2) with increasing temperature. The antiferro-ferromagnetic transition for samples with x≤0.2 can also be induced by an external field. The required field is very low, and decreases with increasing Ga concentration. More Ga concentration (x≥0.3) leads to the samples being ferromagnetic in the whole temperature range below the Curie temperature. The Ga substitution weakens the interlayer magnetic coupling between the Mn spins. Corresponding to the metamagnetic transition, a magnetoresistance as large as 32% under a field of 5 T was observed at 5 K for the sample with x=0.2. 相似文献
7.
Effects of Ga substitution for Sn on the structure and magnetic properties of TbMn6Sn6-xGax (x=0.0-1.2) compounds have been investigated by means of x-ray diffraction, magnetization measurement and 119Sn M?ssbauer spectroscopy. The substitution of Ga for Sn results in a decrease in lattice constants and unit-cell volumes. The magnetic ordering temperature decreases monotonically with increasing Ga content from 423 K for x=0.0 to 390 K for x=1.2. At room temperature, the easy magnetization direction changes from the c-axis to the ab-plane. This variation implies that the substitution of Ga for Sn leads to a decrease in the c-axis anisotropy of the Tb sublattice. An increase in the non-magnetic Ga concentration results in a monotonic decrease of the spontaneous magnetization Ms at room temperature. Since there are three non-equivalent Sn sites, 2c (0.33, 0.67,0), 2d (0.33, 0.67,0.5) and 2e (0,0,0.34) in the TbMn6Sn6-xGax compounds, the 119Sn M?ssbauer spectra of the TbMn6Sn6 and TbMn6Sn5.4Ga0.6 compounds can be fitted by three sextets. The hyperfine fields (HFs) decrease in the order of HF(2d)>HF(2e)>HF(2c), which is in agreement with the magnetic structure. 相似文献
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9.
随着x的增加,多晶La0.6-xGdxSr1.4MnO4(x=0, 0.1, 0.2, 0.4, 0.6)的零场冷却 曲线从类自旋玻璃型转变成顺磁型,并且每条零场冷却 曲线都有一在20K的拐点。这一行为可以从Gd和Mn各自对材料总磁性的不同贡献来理解。另外,在所有的样品中,从100K到室温,都观察到了热激活导电行为。由于Mn-Mn间强的反铁磁耦和,直到外场达到50 kOe,都没有观察到明显的磁电阻效应。 相似文献
10.
铁基纳米复合永磁材料的相成分与磁性 总被引:4,自引:0,他引:4
纳米复合永磁材料由于具有高剩磁,高磁能积,高矫顽力和相对低的稀土含量等优点而有可能成为新一代价格低谦粘结永磁体,文章介绍了纳米复合永磁材料的磁特性,着重讨论了Fe3B基纳米材料相成分与磁性的关系,并证明其永磁性并非来源于Nd2Fe14B永磁相,最后介绍了纳米复合永磁材料的最新进展。 相似文献