Phenomenological model of longitudinal spin fluctuations in itinerant antiferromagnets

Abstract

Abstract. We present the phenomenological analysis of the spectrum of longitudinal spin fluctuations in isotropic itinerant electron antiferromagnets with account of spin anharmonicity giving rise to coupling of transverse and longitudinal normal modes. The spectrum consists of a quasielastic part forming a central peak or a dip, depending on temperature and the Landau relaxation rate. Effects of spin fluctuation coupling also give rise to an inelastic part of the spectrum which has a form of resonances or antiresonances near the magnon frequencies related to non-propagating longitudinal excitations.Essentially, magnetic dynamics in itinerant electron magnets differs from that in

The influence of phonon anharmonicity on thermal and elastic properties of neptunium

“…[1][2][3][4][5]) dedicated to investigation of the actinide metals and their compounds. This can be explained not only by their strategic importance, but also by their unusual physical properties.…”

“…This model enabled to describe the unusual temperature dependenci es of thermal properties of plutoniu m [13] and correctly determine the electronic contributi ons that in case of Pu are also affected by the spin anharmonicity [3,13].…”

Thermodynamic simulation of thermophysical and elastic properties of plutonium

“…The calculation of magnetic, thermophysical, and elastic properties of δ plutonium (for Pu 0.96 Ga 0.04 alloy) in [2,3] showed that the experimentally observed strong temperature dependences of these properties are due to consider able lattice and magnetic anharmonicity (i.e., temper ature dependent spin rigidity). Magnetic anharmon ism of Pu 1 -x Ga x alloys was also detected in [4], where their anomalous expansion is explained on the basis of the spin fluctuation model. There are no indica tions to magnetic anharmonicity of α Pu because its magnetic susceptibility is almost independent of temperature; however, self consistent analysis of the reasons for strong temperature dependences of its thermophysical and elastic properties has not been carried out.…”

“…Here, we confine our anal ysis to the expression derived for the lattice entropy, which will be considered in detail below both of the α Pu and δ Pu: (4) To estimate the effect of spin fluctuations on stabi lization of the δ phase, we will also calculate spin fluctuation entropy . Using the expression for the thermodynamic potential of electrons derived in [3] and the thermodynamic definition of entropy in the self consistent spin fluctuation theory for the δ phase, we obtain…”

“…is the standard "one electron" entropy, is the paramagnetic entropy, m (l) is the ampli tude of spin fluctuations in the lth band (l = f, d), and k (l) is the spin rigidity characterizing the degree of magnetic anharmonicity [3,4].…”