Magnetic structure and phase diagram of TmB4

TL;DR

This study investigates the complex magnetic phases of TmB4, revealing multiple antiferromagnetic states and magnetization plateaus linked to stripe structures, driven by frustration and strong Ising anisotropy.

Contribution

It provides new insights into the magnetic phase diagram of TmB4, identifying specific plateau states and proposing their origin from stripe structures due to frustration.

Findings

Multiple antiferromagnetic phases below 11.7 K.

Observation of magnetization plateaus at 1/2, 1/9, 1/8, and 1/7 of MS.

Stripe structures as domain boundaries between AF ordered blocks.

Abstract

Magnetic structure of single crystalline TmB4 has been studied by magnetization, magnetoresistivity and specific heat measurements. A complex phase diagram with different antiferromagnetic (AF) phases was observed below TN1 = 11.7 K. Besides the plateau at half-saturated magnetization (1/2 MS), also plateaus at 1/9, 1/8 and 1/7 of MS were observed as function of applied magnetic field B//c. From additional neutron scattering experiments on TmB4, we suppose that those plateaus arise from a stripe structure which appears to be coherent domain boundaries between AF ordered blocks of 7 or 9 lattice constants. The received results suggest that the frustration among the Tm3+ magnetic ions, which maps to a geometrically frustrated Shastry-Sutherland lattice lead to strong competition between AF and ferromagnetic (FM) order. Thus, stripe structures in intermediate field appear to be the best way to minimize the magnetostatic energy against other magnetic interactions between the Tm ions combined with very strong Ising anisotropy.