Positive oscillating magnetoresistance in a van der Waals antiferromagnetic semiconductor

TL;DR

This study reveals a unique positive, bias-dependent magnetoresistance with oscillations in thin CrPS4 van der Waals antiferromagnetic semiconductors, driven by transport through in-gap defect states, contrasting prior negative magnetoresistance findings.

Contribution

It demonstrates a novel positive magnetoresistance behavior in CrPS4, linked to space-charge limited transport and defect states, expanding understanding of transport in vdW magnetic semiconductors.

Findings

Positive magnetoresistance observed in CrPS4 devices under bias.

Oscillations in magnetoresistance linked to in-gap defect states.

Transport behavior differs from previously studied layered antiferromagnetic semiconductors.

Abstract

In all van der Waals layered antiferromagnetic semiconductors investigated so far a negative magnetoresistance has been observed in vertical transport measurements, with characteristic trends that do not depend on applied bias. Here we report vertical transport measurements on layered antiferromagnetic semiconductor CrPS$_4$ that exhibit a drastically different behavior, namely a strongly bias dependent, positive magnetoresistance that is accompanied by pronounced oscillations for devices whose thickness is smaller than 10 nm. We establish that this unexpected behavior originates from transport being space-charge limited, and not injection limited as for layered antiferromagetic semiconductors studid earlier. Our analysis indicates that the positive magnetoresistance and the oscillations only occur when electrons are injected into in-gap defect states, whereas when electrons are injected into the conduction band the magnetoresistance vanishes. We propose a microscopic explanation for the observed phenomena that combines concepts typical of transport through disordered semiconductors with known properties of the CrPS$_4$ magnetic state, which captures all basic experimental observations. Our results illustrate the need to understand in detail the nature of transport through vdW magnets, to extract information about the nature of the order magnetic states and its microscopic properties.