Researchers at Xi'an Jiaotong University (XJTU) have made new progress in research on two-dimensional magnetic semiconductors, providing a new method for the detection of the magnetic properties of two-dimensional materials.

Professor Wang Zhe at XJTU and a research team under Professor Alberto Morpurgo at the University of Geneva found that tunneling conductance in a two-dimensional ferromagnetic semiconductor is determined by magnetization, showing that the magnetization of two-dimensional ferromagnets can be accurately measured by electron tunneling.

They prepared a "graphene/chromium tribromide CrBr3/graphene" tunnel junction and systematically measured the conductance of the tunnel junction at different temperatures and with different magnetic fields.

Through analysis, it was found that whether the tunnel junction's magnetic conductance is caused by an external magnetic field above the Curie temperature or caused by the spontaneous magnetic moment below the Curie temperature, there is a unique dependence on the magnetization of the material.

This phenomenon can be explained by the spin-dependent Fowler–Nordheim electron tunneling model. This physical effect indicates that the magnetization of the sample can be deduced from the measurement of tunneling magnetoresistance. 

(a) Diagram of CrBr3 crystal and tunneling junction

(b) Dependence of tunneling magnetic conductance on magnetization, the black line is the theoretical fitting data

(c) Obtaining the magnetization of a two-dimensional magnet by tunneling magnetic conductance

Titled Magnetization dependent tunneling conductance of ferromagnetic barriers, their research results were published in Nature Communications, an open access, multidisciplinary journal dedicated to publishing high-quality research in all areas of the biological, health, physical, chemical and Earth sciences.

XJTU is the first unit and first corresponding unit, and Wang is the first author and co-corresponding author. This research, financed by the National Natural Science Foundation of China, was conducted during Wang's visit to the University of Geneva.

Magnetic materials are an important foundation of modern information storage technology. The writing or reading of information in existing devices is achieved by changing or detecting the magnetic state of magnetic thin film materials.

Two-dimensional magnetic semiconductors are new materials that have both magnetic and semiconductor properties and are only a few atomic layers thick, which can have an important impact on the development of high-density information devices in the future.

Due to the small size of two-dimensional magnetic semiconductors, traditional magnetic measurement methods cannot be used to obtain its magnetic properties. Therefore, it is necessary to explore its new physical effects and apply them to micro-nano-scale magnetic detection.

Link to the paper: https://www.nature.com/articles/s41467-021-26973-7