High-Moment-Low-Moment Description of Magnetovolume Effects in Y(Mn x Al 1− x ) 2 and Y x Sc 1− x Mn 2
Based on the assumption of a high-moment-low-moment instability of the Mn atom, we construct a simple spin model with coupled magnetic and spatial degrees of freedom to describe the Laves phase systems Y(Mn x Al 1 m x ) 2 and Y x Sc 1 m x Mn 2 . Monte Carlo simulations of this model qualitatively reproduce anomalies observed in these materials like a discontinuous giant volume change and anomalous thermal expansion behavior.
Effect of pressure on the Néel temperature of YMn2: resistivity of Y(Mn1−xCux)2
Abstract Resistivity measurements have been carried out for Y(Mn1−xCux)2 compounds with values of x of 0, 0.04, 0.07, 0.10, 0.20 and 0.30 in the temperature range from 4.2 up to 300 K at zero pressure and for YMn2 under a pressure of 2 kbar. TN has been found to decrease rapidly by applying external pressure as well as by applying a chemical pressure caused by a partial substitution of Mn atoms by Cu atoms.
Helimagnetism in the cubic Laves phase YMn2
Abstract Neutron diffraction experiments on YMn 2 using a wave length of λ N = 2.483 A show a splitting of the magnetic peaks. The magnetic structure is helimagnetic consistent with an angle modulation of the previously reported antiferromagnetic structure. The NMR spectrum can be explained as arising from a perturbation of the helix by the magnetocrystalline anisotropy. Below T N the observed frustration of the negative Mn interactions is inherent from the topology of the crystallographic structure. Above T N , it creates short range ordering whose thermal decrease may explain the increase in the paramagnetic neutron scattering as the temperature is increased.