Incommensurate Magnetic Ordered Phase with Enhanced Low-Temperature Magnetic Specific Heat in SmAu${}_3$Al${}_7$

Abstract

Neutron scattering and muon spin rotation ($\hat{I}¼$SR) measurements on single-crystal SmAu${}_3$Al${}_7$ reveal magnetically ordered states associated with successive transitions at $T_{\mathrm{N}}$ = 2.8 K and $T^{\ast }$ = 0.9 K. Magnetic Bragg peaks appear below $T_{\mathrm{N}}$ with an incommensurate (IC) propagation vector $\mathbf{q}$ = (0.30, 0, 1.33). $\hat{I}¼$SR detects spontaneous internal fields below $T_{\mathrm{N}}$, and the spectral shape is consistent with the IC magnetic ordering. No anomalies are observed at $T^{\ast }$, indicating that the magnetic structure remains essentially unchanged below and above $T^{\ast }$. The magnetic order is revealed to be a spatially homogeneous long-range ordered state, rather than a partially disordered state proposed in earlier studies. The possible connection between the IC magnetic order and the enhanced low-temperature magnetic specific heat is discussed.

13 pages, 5 figures