Energy-gap driven low-temperature magnetic and transport properties in Cr${}_{1/3}M$S${}_2$ ($M$ = Nb or Ta)

Abstract

The helimagnets Cr${}_{1/3}M$S${}_2$ ($M$ = Nb or Ta) have attracted renewed attention due to the discovery of a chiral soliton lattice (CSL) stabilized in an applied magnetic field, but reports of unusual low-temperature transport and magnetic properties in this system lack a unifying explanation. Here we present electronic structure calculations that demonstrate the materials are half-metals. There is also a gap-like feature (width in range 40-100 meV) in the density of states of one spin channel. This electronic structure explains the low-temperature electronic and magnetic properties of Cr${}_{1/3}M$S${}_2$ ($M$ = Nb or Ta), with the gap-like feature particularly important for explaining the magnetic behavior. Our magnetometry measurements confirm the existence of this gap. Dynamic spin fluctuations driven by excitations across this gap are seen over a wide range of frequencies (0.1 Hz to MHz) with AC susceptibility and muon-spin relaxation (${\mu }^{+}$SR) measurements. We show further how effects due to the CSL in Cr${}_{1/3}$NbS${}_2$, as detected with ${\mu }^{+}$SR, dominate over the gap-driven magnetism when the CSL is stabilized as the majority phase.

6 pages, 4 figures

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• BoltzTraP. A code for calculating band-structure dependent quantities
• A.C. susceptibility as a probe of low-frequency magnetic dynamics
• Tricritical point and phase diagram based on critical scaling in monoaxial chiral helimagnet Cr1/3NbS2
• Skyrmions in magnetic materials
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Cited by in corpus (2)

• Comparative Electronic Structures of the Chiral Helimagnets Cr1/3NbS2 and Cr1/3TaS2
• Magnetism in $M_{1/3}$NbS${}_2$ ($M$ = Fe, V, Mn): insight into intercalated transition-metal dichalcogenides using $\mu$SR