Extrinsic and intrinsic origins of anisotropic magnetoresistance in doped YIG

Abstract

A microscopic model of Ca : YIG minimal system in the form of a pair of the tetrahedral (d) iron -oxygen clusters, separated by the octahedral (a) cluster, coupled in series to the electrodes, is employed in an interpretation of the experimentally observed intriguing behaviour of anisotropic magnetoresistance (MR). Two possible origins of the anisotropy of MR are viewed. The extrinsic one results from orbital contributions to magnetic moments of the central clusters and reveals itself in the external magnetic field. The intrinsic one is caused by different spin polarisation of the left and the right d clusters with respect to the middle a cluster. The effect is connected with a presence of a compensating hole at one of the tetrahedral clusters.

Spin and Charge Current in a Short Semiconducting Chain of Paramagnetic Ionic Blocks

“…i = 1, 2, 3 labels the ionic blocks and µ = 1, 2, 3, 4 labels their respective eigenstates [1][2][3]. In our convention, m s is the spin number projection, attached to the states µ = 1, 3, whereas −m s is the spin number projection of µ = 2, 4.…”

“…An external magnetic and/or molecular field (B) can significantly change the mutual positions of the cluster's energy levels. Shifts of the energy levels can be computed in the first order of the perturbation theory, considering the Zeeman term as a perturbation, with possible orbital contribution to the magnetic moment [2].…”

“…The method, employed throughout this paper [1,2], is designed for such systems, whose natural building units are ionic clusters. This is true about many semiconducting compounds with permanent magnetic moments, but especially about the transition metal oxides and/or manganites.…”

A model of spin-polarised charge transport in magnetic oxides

“…The explicit expressions for bothĤ c andĤ T will be given below in terms of the standard-basis operators [5][6][7].…”