paper

Fragile singlet ground state magnetism in pyrochlore osmates R2Os2O7 (R=Y and Ho)

arXiv:1602.05121 · doi:10.1103/PhysRevB.93.134426

Abstract

The singlet ground state magnetism in pyrochlore osmates Y $_{2}$ Os $_{2}$ O $_{7}$ and Ho $_{2}$ Os $_{2}$ O $_{7}$ is studied by DC and AC susceptibility, specific heat, and neutron powder diffraction measurements. Despite the expected non-magnetic singlet in the strong spin-orbit coupling (SOC) limit for Os $^{4 +}$ ( $5 d^{4}$ ), Y $_{2}$ Os $_{2}$ O $_{7}$ exhibits a spin-glass (SG) ground state below 4 K with weak magnetism, suggesting possible proximity to a quantum phase transition between the non-magnetic state in the strong SOC limit and the magnetic state in the strong superexchange limit. Ho $_{2}$ Os $_{2}$ O $_{7}$ has the same structural distortion as occurs in Y $_{2}$ Os $_{2}$ O $_{7}$ . However, the Os sublattice in Ho $_{2}$ Os $_{2}$ O $_{7}$ shows long-range magnetic ordering below 36\,K. The sharp difference of the magnetic ground state between Y $_{2}$ Os $_{2}$ O $_{7}$ and Ho $_{2}$ Os $_{2}$ O $_{7}$ signals the singlet ground state magnetism in $R_{2}$ Os $_{2}$ O $_{7}$ is fragile and can be disturbed by the weak $4 f - 5 d$ interactions.

7 pages, 6 figures