Neutron diffraction study on the two-dimensional Ising system KEr(MoO4)2

The magnetic properties of the two-dimensional Ising antiferromagnet KEr(MoO4)(2) have been investigated below and above transition temperature T-N similar to 0.95 K in zero field and in fields up to 6.5 T by means of elastic neutron-diffraction, heat-capacity, and magnetization measurements. The low-temperature signal recorded at 0.34 K by neutron diffraction is explained within a noncollinear magnetic structure model. However, additional contribution is also present when applying the external magnetic field along the c axis even at temperatures well above the magnetic transition temperature T-N. Various explanations are discussed.