First-Order Phase Transition in Europium Metal

Abstract

On the basis of our experiments, we cannot interpret the results with the model of the random flipping of the hyperfine field. 1 (The sidebands observed at 4 Mc/sec could not possibly be detected in supermalloy samples, as in Perlow's experiment, because of the large width of the Mossbauer lines at £T rf = 0.) Furthermore, the calculation of x 2 given above for the case of iron has been carried out also for supermalloy samples. The relatively smaller values of k 2 for the latter can be compensated by the relatively larger magnetic energy density. Consequently, the model of the magnetostriction might be valid for supermalloy, if it is for iron.In conclusion, the present experiments yield the following information:(a) The sidebands observed in iron slabs of various thicknesses in the presence of a rf magnetic field cannot be described by a single "modulation index"; a quantum-mechanical derivation of their spectrum accounts satisfactorily for the obtained results.(b) The dependence of the intensity of the sidebands on the static magnetic field HQ, perpendicular to H T i, suggests that the domain-wall contribution, if any, to the observed effect is much smaller than the contribution of the rotation of domain magnetization.(c) The magnetostriction model accounts for the intensity of the sidebands, if the magneto-elastic coupling coefficient k 2 is assumed to be much larger in the dynamic condition than in the static condition.We have used Mossbauer-effect measurements of the hyperfine (hf) interaction in Eu metal to study the behavior of its sublattice magnetization in the vicinity of the magnetic ordering temperature. At 88.6°K, the hf field falls from 0.4 of the saturation value to zero. This results from the existence of a first-order transition coincident with the magnetic ordering. The possible causes of the transition are discussed. The temperature dependence of the hyperfine field just below the transition is analyzed in terms of criticalpoint theory. The results of thermal-expansion measurements are also presented and discussed.

Magnetism of europium under extreme pressures

“…At ambient pressure Eu orders antiferromagnetically at T N = 90 K [18][19][20][21] accompanied by a tetragonal deformation of the bcc lattice [22]. All lanthanide metals except Eu and Yb are trivalent at ambient pressure.…”

Magneto-elastic coupling across the first-order transition in the distorted kagome lattice antiferromagnet Dy3Ru4Al12

“…Several systems are known to display first-order transitions from a magnetically disordered into an antiferromagnetic state that originate from magnetoelastic coupling [22,26]. Such transitions in Eu and in EuSn 3 were shown to be due to the strain-induced exchange interactions, although the relative thermal expansion at the phase transformation was found to be relatively low, ~1×10 -4 , for both systems [22,26]. A somewhat larger Δ l / l ~ 5.6×10 -4 was reported for the compound MnSe where the strong dependence of the net exchange interaction from the lattice parameters also plays the principal role [27].…”

Magnetic properties of Dy nano-islands on graphene

“…The √ 3 × √ 3 phase is practically a ferromagnet with the easy axis normal to the plane and the in-plane magnetization being 20 times lower than the magnetization along the normal direction. Bulk Eu undergoes a first order PM-AFM transition at T N = 88.4 K [20]. In addition, previous experiments on isolated transition metal adatoms on graphene have shown lower magnetic moments than those in bulk environment [21] as a result of strong hybridization with the carbon atoms.…”