Neutron diffraction and electrical transport studies on the incommensurate magnetic phase transition in holmium at high pressures

Abstract

Neutron diffraction and electrical transport measurements have been made on the heavy rare earth metal holmium at high pressures and low temperatures in order to elucidate its transition from a paramagnetic (PM) to a helical antiferromagnetic (AFM) ordered phase as a function of pressure. The electrical resistance measurements show a change in the resistance slope as the temperature is lowered through the antiferromagnetic Néel temperature. The temperature of this antiferromagnetic transition decreases from approximately 122 K at ambient pressure at a rate of -4.9 K GPa(-1) up to a pressure of 9 GPa, whereupon the PM-to-AFM transition vanishes for higher pressures. Neutron diffraction measurements as a function of pressure at 89 and 110 K confirm the incommensurate nature of the phase transition associated with the antiferromagnetic ordering of the magnetic moments in a helical arrangement and that the ordering occurs at similar pressures as determined from the resistance results for these temperatures.

Revisiting the magnetic structure of Holmium at high pressure by using neutron diffraction

“…Recently, the new available extreme conditions neutron diffractometers have facilitated the study of the high pressure region of Holmium. In 2012, Thomas et al 14 performed neutron diffraction experiments at maximum pressures of 6.6 GPa at 89, 110 and 300 K. They established the incommensurate nature of the HM phase and determined the decrease of T N from approximately 122 K at AP at a rate of -4.9 K/GPa up to a pressure of 9 GPa, above which the PM to HM transition vanishes, in agreement with Ref. 21,31 .…”

“…This could destabilize the HM state giving place to a FM ground state. Hereafter, the magnetic transition temperatures between the FM and HM states and between the HM and the paramagnetic (PM) states are denoted as T C and T N , respectively.The structure of all 4f-lanthanide FM metals is hexagonal closed packed, hcp, with stacking unit ABA at ambient pressure (AP), and exhibit the structural transformations in the sequence hcp (ABA) → Sm-type (ABABCB-CACA) → double-hcp (dhcp) (ABACA) → fcc (ABCA) → trigonal under increasing pressure 6,7 .The evoution of the magnetic properties with the structural transformations in 4f-lanthanide metals has been studied theoretically 8 and reported experimentally by magnetic characterization [9][10][11][12][13] , electrical resistivity 14-20 , neutron diffraction 14,16,[21][22][23][24][25] , X-ray diffraction 26 , and Mössbauer spectroscopy 27 . In particular, neutron diffraction experiments have been successfully employed to study the magnetic phases of Ho metal at high pressures and variable temperatures, as we briefly summarize in the next paragraph.The first neutron scattering experiment in this metal was performed at AP by Koehler et al 28 .…”

“…The evoution of the magnetic properties with the structural transformations in 4f-lanthanide metals has been studied theoretically 8 and reported experimentally by magnetic characterization [9][10][11][12][13] , electrical resistivity 14-20 , neutron diffraction 14,16,[21][22][23][24][25] , X-ray diffraction 26 , and Mössbauer spectroscopy 27 . In particular, neutron diffraction experiments have been successfully employed to study the magnetic phases of Ho metal at high pressures and variable temperatures, as we briefly summarize in the next paragraph.…”