Researchers using the HP-CAT 16-BM-D beamline at the APS have performed experiments on ferromagnetic LaCo5 that 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.
Coupled degrees of freedom are at the root of the emergent behaviors of functional materials. Through their interconnected responses, lattice, electronic, magnetic, and orbital degrees of freedom can manifest physical effects ranging from superconductivity to ferroelectricity to magnetocaloric properties.
We have performed high-pressure magnetotransport and x-ray diffraction measurements on ferromagnetic LaCo5 , confirming the theoretically predicted electronic topological transition driving the magnetoelastic collapse seen in the related compound YCo5. Our x-ray diffraction results 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 coupling of the electronic, magnetic, and lattice degrees of freedom is further substantiated by the evolution of the anomalous Hall effect, which couples to the magnetization of the ordered state of LaCo5.
Ryan L. Stillwell, Jason R. Jeffries, Scott K. McCall, Jonathan R. I. Lee, Samuel T. Weir and Yogesh K. Vohra, “Strongly Coupled Electronic, Magnetic and Lattice Degrees of Freedom in LaCo5 Under Pressure,” Physical Review B, 92, 174421, DOI: 10.1103/PhysRevB.92.174421, Published Online November 4, 2015.