Topological magnetic phase transition in Eu-based A-type antiferromagnets

Abstract

Recently, a colossal magnetoresistance (CMR) was observed in EuCd${}_2$P${}_2$ -- a compound that does not fit the conventional mixed-valence paradigm. Instead, experimental evidence points at a resistance driven by strong magnetic fluctuations within the two-dimensional ($2d$) ferromagnetic (FM) planes of the layered antiferromagnetic (AFM) structure. While the experimental results have not yet been fully understood, a recent theory relates the CMR to a topological vortex-antivortex unbinding, i.e., Berezinskii-Kosterlitz-Thouless (BKT), phase transition. Motivated by these observations, in this work we explore the magnetic phases hosted by a microscopic classical magnetic model for EuCd${}_2$P${}_2$, which easily generalizes to other Eu A-type antiferromagnetic compounds. Using Monte Carlo techniques to probe the specific heat and the helicity modulus, we show that our model can exhibit a vortex-antivortex unbinding phase transition. We find that this phase transition displays the same sensitivity to in-plane magnetization, interlayer coupling, and easy-plane anisotropy that is observed experimentally in the CMR signal, providing qualitative numerical evidence that the effect is related to a magnetic BKT transition.

8 pages, 4 figures

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Cited by in corpus (6)

• Colossal magnetoresistance in EuZn${}_2$P${}_2$ and its electronic and magnetic structure
• Spin-carrier coupling induced ferromagnetism and giant resistivity peak in EuCd${}_2$P${}_2$
• Electronic band reconstruction across the insulator-metal transition in colossal magnetoresistive EuCd2P2
• Engineering of a Layered Ferromagnet via Graphitization: An Overlooked Polymorph of GdAlSi
• Recent advances in understanding and manipulating magnetic and electronic properties of Eu$M_2{X}_2$ ($M$ = Zn, Cd; $X$ = P, As)
• Spin-qubit Noise Spectroscopy of Magnetic Berezinskii-Kosterlitz-Thouless Physics