Coupled electronic, magnetic, and lattice degrees of freedom in LaCo5

Figure caption. A marked deviation in the pressure dependence of the c-axis near the predicted isomorphic collapse near 10 GPa.
Figure caption. A marked deviation in the pressure dependence of the c-axis near the predicted isomorphic collapse near 10 GPa.

Coupled degrees of freedom are at the root of the emergent behaviors of functional materials. Through their interconnected responses, electronic, magnetic, and lattice degrees of freedom can manifest physical effects ranging from superconductivity to ferroelectricity to magnetocaloric properties. Recent HPCAT experiments on ferromagnetic LaCo5 show an anisotropic lattice collapse of the c axis near 10 GPa that is also commensurate with a change in the majority charge carriers evident from high-pressure Hall effect measurements. The theoretical calculations predicted that there would be magnetic and electronic transitions accompanying the observed anisotropic lattice collapse. Indeed, associated changes in the electronic structure and magnetic response were measured via high-pressure magnetotransport, which revealed a change in carrier type and a sharp increase in the amplitude of the anomalous Hall effect at 9.3 GPa. The coupling of the electronic, magnetic, and lattice degrees of freedom is further substantiated by the evolution of the anomalous Hall effect. (R. L. Stillwell, et al, Phys. Rev. B, 92, 174421, 2015)