Magnetic Structure and Phase Diagram of TmB₄

Abstract

Magnetic structure of single crystalline TmB 4 has been studied by magnetization, magnetoresistivity, and specific heat measurements. A complex phase diagram with different antiferromagnetic phases was observed below T N1 = 11.7 K. Besides the plateau at half-saturated magnetization (1/2 M S ), also plateaus at 1/9, 1/8 and 1/7 of MS were observed as a function of applied magnetic field B c. From additional neutron scattering experiments on TmB4, we suppose that these plateaus arise from a stripe structure which appears to be coherent domain boundaries between antiferromagnetic-ordered blocks of 7 or 9 lattice constants. The received results suggest that the frustration among the Tm 3+ magnetic ions, which maps to a geometrically frustrated Shastry-Sutherland lattice, leads to a strong competition between antiferromagnetic and ferromagnetic order. Thus, stripe structures in intermediate field appear to be the best way to minimize the magnetostatic energy against other magnetic interactions among the Tm ions combined with very strong Ising anisotropy.PACS numbers: 75.30.Kz, 75.25.+z IntroductionRare earth tetraborides REB 4 crystallize in a tetragonal structure with the space group P 4/mbm, where the RE ions map to a Shastry-Sutherland type geometrically frustrated lattice (SSL) in the c-plane. It was shown that all heavy REB 4 (RE = Tb, Dy, Ho, Er, Tm) exhibit a strong Ising-like anisotropy which orients the RE magnetic moments along the c-axis, and complex phase dia-

Hysteretic magnetoresistance and unconventional anomalous Hall effect in the frustrated magnetTmB4

“…3(a) as a function of magnetic flux density B = µ 0 H + M [12], displays the previously reported plateau structure [13][14][15]. ρ xx at 2K (Fig.…”

“…[16]. Frustration in TmB 4 is reflected in the moderately large frustration parameter [15,19] and in the appearence of a diffuse peak in neutron scattering above T N 2 [16], indicative of shortrange order. In the temperature range T N 1 > T > T N 2 , the diffuse peak coexists with the sharp peaks from MP1 and MP2 [16].…”

“…1(b)). While other frustrated Archimedean lattices such as the triangular and Kagomé lattices are well studied [10,11], the RB 4 family is the only known realization of the Archimedean Shastry-Sutherland lattice.In this article, we use magnetization and transport experiments to study TmB 4 , a member of the RB 4 family that has attracted attention for its rich phase diagram [13][14][15][16] (Fig. 1(c)).…”

“…We suggest that subtle changes occur in the magnetic structure of TmB 4 that strongly influence the MR but not the bulk magnetization. Neutron scattering experiments have shown that the magnetic structure in the modulated and the plateau phases consists of stripes or domains [14][15][16]. However, the microscopic structure at the domain walls is unknown.…”

Magnetization process in the classical Heisenberg model on the Shastry-Sutherland lattice

“…This sublattice is again topologically equivalent to the SSL (see Fig. 1 18,19,20,21 In this paper we investigate classical Heisenberg spins on the SSL under a magnetic field. Note that we are not aware of any previous study of the classical limit in the presence of a magnetic field, although some of the first studies of the zero-field properties of the SSL did start from this limit.…”