Frustration induced dimensional reduction and coexistence of long and short-range magnetic order in NdCl${}_3$

Abstract

The phenomenon of frustration greatly enriches the accessible physics of quantum magnets. With this in mind we study the magnetism of NdCl${}_3$ using a combination of bulk properties measurements and neutron scattering techniques. The low-temperature heat capacity reveals two magnetic transitions at $T_{N1}$ = 270 mK and $T_{N2}$ = 180 mK. However, much of the magnetic entropy is released above $T_{N1}$, manifesting as a broad peak centered at $T^{\ast }\approx$ 450 mK. Single crystal elastic neutron scattering reveals highly anisotropic magnetic diffuse scattering above $T_{N2}$, confirming that quasi-one-dimensional, short-range, antiferromagnetic order is the origin of the broad peak in the heat capacity. Magnetic Bragg peaks characterized by a $\vec{k}$ = ($0$ $0$ $\frac{1}{2}$) propagation vector emerge below $T_{N1}$. Interestingly, the magnetic diffuse scattering persists for $T_{N2}<T<T_{N1}$, indicating a regime of coexisting short and long-range order. The magnetic Bragg peaks exhibit an additional increase in intensity below $T_{N2}$ with no change in $\vec{k}$. Concomitantly, the diffuse scattering disappears indicating the attainment of full long-range order. While the precise nature of the ordered magnetic ground state remains unresolved, the observed magnetic scattering indicates predominate $c$-axis moments with a small $ab$-plane component. We propose that the quasi-one-dimensional behavior and the coexistence of short and long-range order are driven by frustration of anisotropic exchange interactions.

15 pages, 6 figures, 2+A1 tables, submitted to Physical Review B