Sequential Cobalt Magnetization Collapse in ErCo2: Beyond the Limits of Itinerant Electron Metamagnetism

Abstract

The itinerant electron metamagnetism (IEM) is an essential physical concept, describing magnetic properties of rare earth – transition metal (R-TM) intermetallics, demonstrating technologically important giant magnetoresistance and magnetocaloric effects. It considers an appearance of TM magnetization induced by spontaneous magnetization of surrounding R atoms, which provides significant response of the magnetic and transport properties on variation of external parameters (temperature, pressure, magnetic field) due to strong coupling between magnetic sublattices. The RCo2 compounds were generally considered as model systems for understanding of basic properties of IEM intermetallics. However, microscopic nature of magnetic properties still remains unclear. In our experimental and theoretical study of ErCo2 in a wide range of thermodynamic parameters a sequential collapse of cobalt sublattice magnetization in the background of nearly unchanged Er sublattice magnetization was revealed. The uncoupled magnetizations behavior challenges the IEM concept applicability and evidences more complex nature of magnetism in ErCo2 and related RCo2 systems.

Negative Thermal Expansion in the Materials With Giant Magnetocaloric Effect

“…In the cubic C15 structure, rare atoms locate at sites 8(a) (0.125, 0.125, 0.125) and Co atoms at sites 16(d) (0.5, 0.5, 0.5) (Figure 14A; Ouyang et al, 2005a). With temperature decreasing, ErCo 2 and TbCo 2 exhibit a rhombohedral distortion (space group R$\overline{3}$m) below Curie temperature T C (Ouyang et al, 2005a; Kozlenko et al, 2015). At low temperature, Er (Tb), Co1, and Co2 atoms occupy Wyckoff sites 6c (0, 0, z), 3b (0, 0, 0.5) and 9e (0.5, 0, 0), respectively.…”

Distribution of Transition Temperatures in Magnetic Transformations: Sources, Effects and Procedures to Extract Information from Experimental Data

“…For high pressures, the linear decrease of the transition temperature with pressure is lost for RE = Ho and Er, becoming pressure independent above 4 GPa [70]. This has been ascribed to the collapse of the Co magnetic moment sublattice, whereas RE sublattice remains almost unchanged with pressure [71].…”

Giant spontaneous resistivity jumps in La0.825Ce0.175Fe12B6

“…Itinerant electron metamagnetism (IEM) is an essential physical phenomenon, depicting magnetic behaviors of some 3d-4f intermetallic compounds, manifesting potentially important functionalities such as colossal magnetoresistance, large magnetostriction and giant magnetocaloric effects [1][2][3][4] . One interesting example of IEM is LaFe12B6 intermetallic which occupies a special place among rare-earth iron-rich compounds.…”