Low-temperature magnetic ordering inSrEr2O4

Abstract

${\text{SrEr}}_{2}{\text{O}}_{4}$ has been characterized by low-temperature powder neutron diffraction, as well as single-crystal specific-heat and magnetization measurements. Magnetization measurements show that the magnetic system is highly anisotropic at temperature above ordering. A magnetic field of 280 kOe applied at $T=1.6\text{ }\text{K}$ does not overcome the anisotropic magnetization and fails to fully saturate the system. Long-range antiferromagnetic ordering develops below ${T}_{N}=0.75\text{ }\text{K}$, identified by magnetic Bragg reflections with propagation vector $\mathbf{k}=0$ and a lambda anomaly in the specific heat. The magnetic structure consists of ferromagnetic chains running along the $c$ axis, two adjacent chains being stacked antiferromagnetically. The moments point along the $c$ direction, but only one of the two crystallographically inequivalent Er sites has a sizeable ordered magnetic moment, $4.5{\ensuremath{\mu}}_{\text{B}}$ at 0.55 K. The magnetic properties of ${\text{SrEr}}_{2}{\text{O}}_{4}$ are discussed in terms of the interplay between the low dimensionality, competing exchange interactions, dipolar interactions, and low-lying crystal-field levels.