Importance of Paramagnetic Background Subtraction for Determining the Magnetic Moment in Epitaxially Grown Monolayer and Few-Layer van der Waals Magnets

TL;DR

This paper emphasizes the importance of proper paramagnetic background subtraction in accurately measuring the magnetic moments of monolayer and few-layer van der Waals magnets, using MnSe2 as a case study.

Contribution

It demonstrates that considering paramagnetic background signals is crucial for correct magnetic moment determination in 2D magnets, correcting previous overestimations.

Findings

Normal diamagnetic subtraction overestimates magnetic moments.

Unintentional Mn doping introduces paramagnetic signals.

Correct background subtraction yields magnetic moments consistent with theory.

Abstract

Due to the atomically thin nature of monolayer and few-layer van der Waals magnets, the undesired background signal from the substrate can have significant contribution when characterizing their magnetic properties. This brings challenges in accurately determining the magnitude of the magnetic moment of the epitaxially grown van der Waals magnets on bulk substrates. In this paper, we discuss the impact of the background subtraction method for accurately determining the magnetic moments in such systems. Using the recently reported intrinsic two-dimensional (2D) van der Waals ferromagnet MnSe${_2}$ as an example, we show that a normal diamagnetic background subtraction method in analyzing the bulk magnetometry measurement will result in an unexpectedly large magnetic moment (greater than ~10 {\mu}${_B}$ per formula unit). Through our systematic growth study, we identify an additional paramagnetic signal due to unintentional Mn doping of the substrate. To extract the correct magnetic moment, a paramagnetic background should also be considered. This yields a total magnetic moment of ~4 {\mu}${_B}$ per formula unit in monolayer MnSe${_2}$, which is in close agreement to the theoretically predicted value.