Abstract
We report a charge-transfer mechanism in tuning of magnetism of Nd-substituted Gd5-xNdxSi4 (x=1 and 2.5) compounds. The X-ray absorption near edge structure measurements demonstrated that Nd substitutions for Gd induce charge transfer of 5d electrons from Gd to Nd. The charge transfer weakens spin-orbital coupling of Gd but strengthens that of Nd. Consequently, the magnetization responses of the substituted compounds to low magnetic fields are increased while their saturation magnetization is reduced. Electronic structure calculations showed that the charge transfer stabilizes a ferromagnetic and a ferrimagnetic structure in the compounds with x = 1 and 2.5, respectively, but that it does not change the 5d–3p hybridization significantly. It is suggested that the charge transfer of 5d electrons may occur in other rare earth-substituted Gd5Si4 compounds allowing for tuning of their magnetism.
Highlights
A variety of interesting phenomena such as a giant magnetocaloric effect, giant magnetostriction and large magnetoresistance were observed in Gd5Si2Ge2 near room temperature.[1,2,3] Those phenomena are related to a magnetostructural transition of this compound from a paramagnetic monoclinic structure to a ferromagnetic orthorhombic structure.[4]
First principle calculations and X-ray magnetic circular dichroism measurements showed that apart from the interslab T–T bonds, intraslab Gd–T bonds play a crucial role in the RKKY interaction of Gd5T4-type compounds.[8,9,10,11,12,13,14,15,16]
The enlargement is anisotropic and is largest along the b and c axes at x = 1 and 2.5, respectively. This anisotropy is related to different Nd occupation as suggested by the first principle calculations below
Summary
A variety of interesting phenomena such as a giant magnetocaloric effect, giant magnetostriction and large magnetoresistance were observed in Gd5Si2Ge2 near room temperature.[1,2,3] Those phenomena are related to a magnetostructural transition of this compound from a paramagnetic monoclinic structure to a ferromagnetic orthorhombic structure.[4]. Apart from different numbers of 4f electrons, R atoms of different species may have different numbers of 5d electrons For this latter difference, charge transfer may occur between the base and substituting R atoms and brings about a change of the electronic structure and magnetism of the compounds. Charge transfer may occur between the base and substituting R atoms and brings about a change of the electronic structure and magnetism of the compounds This potential effect was hinted at by observations of different magnetism in Eu-substituted Gd5Ge427 and in Gd-substituted Er5Si4.20 the role of the charge transfer of 5d electrons in tuning of the magnetism is not understood yet. We investigated charge transfer of 5d electrons and its influence on the electronic and magnetic structures in Nd-substituted Gd5Si4 compounds to unveil this role
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