Grain-size dependent high-temperature ferromagnetism of polycrystalline MnxSi1-x (x~0.5) films

TL;DR

This study investigates how grain size influences high-temperature ferromagnetism in polycrystalline MnxSi1-x films, revealing a complex interplay between interfacial nanocrystalline layers and defect-induced magnetic order.

Contribution

It demonstrates the dependence of ferromagnetic properties on grain size and growth conditions in MnxSi1-x films, highlighting the role of nanocrystalline layers and defect-induced magnetism.

Findings

High-temperature ferromagnetism with TC ~ 370 K observed.

Layered structure with distinct magnetic behaviors at different temperatures.

Sign change in anomalous Hall effect below 30 K.

Abstract

We present the results of a comprehensive study of magnetic, magneto-transport and structural properties of nonstoichiometric MnxSi1-x (x=0.51-0.52) films grown by the Pulsed Laser Deposition (PLD) technique onto Al2O3(0001) single crystal substrates at T = 340{\deg}C. A highlight of our PLD method is the using of non-conventional (shadow) geometry with Kr as a scattering gas during the sample growth. It is found that studied films exhibit high-temperature (HT) ferromagnetism (FM) with the Curie temperature TC ~ 370 K accompanied by positive sign anomalous Hall effect (AHE); they also reveal the layered polycrystalline structure with a self-organizing grain size distribution. The HT FM order is originated from the bottom interfacial nanocrystalline layer, while the upper layer possesses the low temperature (LT) type of FM order with TC = 46 K, gives essential contribution to the magnetization below 50 K and is homogeneous on the nanometer size scale. Under these conditions, AHE changes its sign from positive to negative at T < 30 K. We attribute observed properties to the synergy of self-organizing distribution of MnxSi1-x crystallites in size and peculiarities of defect-induced FM order in PLD grown polycrystalline MnxSi1-x (x~0.5) films.