Magneto-structural properties of Ho₃Co (at ambient and under high pressure)

Srikanta Goswami, M. S. Henriques, V. Petříček, P. D. Babu

R₃T (R = rare earth and T = transition metals) type of rare earth rich intermetallic compounds possess highest R content in the R-T binary family and exhibit various interesting magnetic properties emerging out of their complex magnetic structures. These compounds crystallize in the orthorhombic crystal symmetry with Pnma space group. Ho₃Co is an interesting case, in this family, that has been studied in the present experimental work based on bulk magnetic measurements such as: dc magnetization, specific heat, ac-susceptibility and also microscopically by neutron powder diffraction. Bulk magnetic measurements at ambient condition suggest that the magnetic structure below the Néel temperature at T_N (= 21 K) changes continuously until another antiferromagnetic (AFM) transition occurs at T_t (= 9 K). The incommensurately modulated magnetic structures of this compound at different temperatures were solved by magnetic superpace formalism. The magnetic superspace group describing the spin configuration realized in Ho₃Co explains the evolution of the structures with temperature and supports the speculations drawn from the bulk magnetic measurements. Below T_t, the magnetic modulation is anharmonic. Further, frequency dependent experiments reveal the coexistence of spin glass like states with non-collinear AFM order at low temperature. Externally applied pressure wipes out the low temperature magnetic transition at T_t. The AFM interactions are strengthened with increasing pressure at low temperature while the weak signature of spin glass like state remains up to 1.10 GPa.