Itinerant electron metamagnetism for lattices with van Hove density-of-states singularities near the Fermi level

Abstract

Itinerant-electron metamagnetism is investigated within the Hubbard model for various lattices having van Hove singularities (vHS) in the electronic spectrum: face-centered cubic and orthorhombic lattices. The remarkable itinerant-electron metamagnetic transition occurs provided that the Fermi level is in the region with a strong positive curvature of the density of electron states typically positioned between two close van Hove singularities. Orthorhombic distortion of a~tetragonal lattice is a promising mechanism for generating two closely split vHS with strong density-of-states curvature between them. A phase diagram in terms of electron filling and Hubbard interaction parameter is presented, which shows the paramagnetic-metamagnetic-ferromagnetic phase transition and regions of saturated and non-saturated magnetism. The standard Landau theory expansion based on~the~electron density of states in the vicinity of the Fermi level is demonstrated to be insufficient to describe the whole magnetic phase diagram including the itinerant-electron metamagnetic transition.