Jiangying Yu

Synthesis and exchange bias effect of single-crystalline SrMn3O6−δ nanoribbons

Single-crystalline SrMn3O6−δ nanoribbons (width of 30–500 nm and lengths of up to several hundred micrometers) are synthesized by a molten-salt method. In contrast with the antiferromagnetism in bulk SrMn3O6−δ, magnetization measurements show weak ferromagnetism in these nanoribbons at low temperature. In particular, a notable exchange-bias effect, which strongly depends on the cooling field, is observed in applied magnetic field H≤5 kOe. These results suggest that the exchange bias in the SrMn3O6−δ nanoribbons can be effectively tuned by the cooling field, which is of very special interests for applications.

Composition anisotropy compensation and magnetostriction in Pr(Fe1-xCox)1.9 (0≤x≤0.5) cubic Laves alloys

Polycrystalline magnetostrictive alloys Pr(Fe1−xCox)1.9 (0⩽x⩽0.5) with cubic Laves phase were synthesized by high-pressure annealing. Measurements of Curie temperature, easy magnetic direction (EMD), and magnetostriction were made on these alloys. The EMD of the alloys rotates continuously from ⟨111⟩ for x=0.0 to ⟨110⟩ for x=0.3 and then shows a tendency to ⟨111⟩ with further increasing x. Two magnetostriction peaks at low fields are observed around x=0.2 and x=0.4 due to the lower anisotropy of these two alloys, which is consistent with the variation of EMD. This work demonstrates that the composition anisotropy compensation can be realized in Pr(Fe1−xCox)1.9 system.

Mn substitution effect on the magnetic properties of PrFe1.9 alloy

Polycrystalline magnetostrictive alloys Pr(Fe1−xMnx)1.9 (0⩽x⩽0.2) were synthesized by high-pressure annealing. X-ray diffraction results show that all the samples exhibit cubic Laves phase with MgCu2-type structure. The lattice parameter increases with increasing Mn concentration while the Curie temperature decreases. The saturation magnetization decreases with increasing Mn concentration, which can be understood on the basis of the rigid band model. The magnetizations of the samples with x=0.05 and x=0.1 are easy to get saturated in comparison with that of the sample without Mn, which implies that small amount of substitution Mn for Fe can lower the magnetic anisotropy of the alloy. The saturation magnetostriction decreases monotonously with increasing Mn content, while the magnetostriction of the sample with x=0.1 shows a peak at low magnetic fields.

Impact of postgrowth annealing on spin-glass ordering and exchange bias in SrMn3O6−δ nanoribbons

The magnetic properties of as-grown single-crystal SrMn3O6−δ nanoribbons synthesized by a simple molten-salt method can be significantly improved by a heat-treatment procedure, which enhances the ferromagnetism and spin-glass behavior. These enhanced properties might originate from a spin structure modulated by the thermodynamical equilibrium nonuniform oxygen distribution. Measurements of ac susceptibility prove the existence of a spin-glass phase in the postgrowth annealing SrMn3O6−δ nanoribbons, which differs from the only antiferromagnetic phase in the corresponding bulk material. Asymmetric magnetization hysteresis loops observed in applied magnetic fields H≤5 T are attributed to an exchange coupling between the spin-glass shell and the antiferromagnetic core of postgrowth annealing SrMn3O6−δ nanoribbons. Results suggest that the intrinsic phase inhomogeneity due to the surface effects of the nanostructural manganites may induce exchange anisotropy, which is of special interests for potential applica...

Synthesis and magnetostriction of TbxPr1−x(Fe0.8Co0.2)1.9 cubic Laves alloys

Polycrystalline magnetostrictive alloys TbxPr1−x(Fe0.8Co0.2)1.9 (0≤x≤0.4) which cannot be obtained under normal pressure were synthesized by high-pressure annealing. Measurements of crystal structure, Curie temperature, magnetization, and magnetostriction were made on TbxPr1−x(Fe0.8Co0.2)1.9 alloys. X-ray diffraction results show that the alloys exhibit C15 cubic Laves phase with MgCu2-type structure. The lattice parameter decreases with increasing Tb concentration, while the Curie temperature increases. Because of the antiparallel magnetic moment of Tb and Pr, the saturation magnetization decreases with increasing Tb concentration. The magnetostriction of Tb0.05Pr0.95(Fe0.8Co0.2)1.9 shows a peak at low magnetic fields, while that of Tb0.4Pr0.6(Fe0.8Co0.2)1.9 exhibits a minimum in the whole range of magnetic fields.