X-ray Photoemission Spectroscopy Study of Uniaxial Magnetic Anisotropy Induced in a Ni Layer Deposited on a LiNbO3 Substrate.

Akinobu Yamaguchi,Satoru Suzuki,Tsunemasa Saiki,Keisuke Yamada,Aiko Nakao,Yuichi Utsumi,Masaki Oura,Takuo Ohkochi

doi:10.3390/nano11041024

Abstract

The competition between magnetic shape anisotropy and the induced uniaxial magnetic anisotropy in the heterojunction between a ferromagnetic layer and a ferroelectric substrate serves to control magnetic domain structures as well as magnetization reversal characteristics. The uniaxial magnetic anisotropy, originating from the symmetry breaking effect in the heterojunction, plays a significant role in modifying the characteristics of magnetization dynamics. Magnetoelastic phenomena are known to generate uniaxial magnetic anisotropy; however, the interfacial electronic states that may contribute to the uniaxial magnetic anisotropy have not yet been adequately investigated. Here, we report experimental evidence concerning the binding energy change in the ferromagnetic layer/ferroelectric substrate heterojunction using X-ray photoemission spectroscopy. The binding energy shifts, corresponding to the chemical shifts, reveal the binding states near the interface. Our results shed light on the origin of the uniaxial magnetic anisotropy induced from the heterojunction. This knowledge can provide a means for the simultaneous control of magnetism, mechanics, and electronics in a nano/microsystem consisting of ferromagnetic/ferroelectric materials.

Highlights

The heterojunction, or heterointerface, is of great importance in a wide range of applications, such as thermal-barrier coatings, nanocomposites, electronic and optical devices, giant magnetoresistive and magnetic tunnel junctions, various catalysts, and batteries
We found that uniaxial magnetic anisotropy was induced in the Ni layer on the LiNbO3 substrate due to the formation of the heterojunction; the uniaxial magnetic anisotropy forced the Ni magnetizations to stochastically align parallel or antiparallel to the X-axis of the LiNbO3 substrate (indicated by an arrow in region (i) of Figure 1b)
As previously reported [33,34,35,36,37,38], a stripe domain structure is naturally formed when the wire is aligned perpendicular to the X-axis of the LiNbO3 substrate, even in the absence of an external magnetic field, due to the competition between magnetic shape anisotropy and uniaxial magnetic anisotropy induced by the heterojunction (region (ii) of Figure 1b) [33,34,35,36,37,38]

Summary

Introduction

The heterojunction, or heterointerface, is of great importance in a wide range of applications, such as thermal-barrier coatings, nanocomposites, electronic and optical devices, giant magnetoresistive and magnetic tunnel junctions, various catalysts, and batteries. As previously reported [33,34,35,36,37,38], a stripe domain structure is naturally formed when the wire is aligned perpendicular to the X-axis of the LiNbO3 substrate, even in the absence of an external magnetic field, due to the competition between magnetic shape anisotropy and uniaxial magnetic anisotropy induced by the heterojunction (region (ii) of Figure 1b) [33,34,35,36,37,38]. The XMCD spectrum of the Ni layer on the LiNbO3 substrate in Figure 1d was obtained by taking the difference between the X-ray absorption spectra (XAS) spectra extracted from the white (magnetization parallel to X-ray) and black (antiparallel) regions. XMCD spectra of Ni wire calculated from the subtraction of [XAS: pW-nB] − [XAS: pB-nB]

Sample Fabrication and Methods

Results and Discussion

81 Fe19 layer

Conclusions