Ordering in the dilute weakly-anisotropic antiferromagnet Mn(0.35)Zn(0.65)F2

TL;DR

This study uses neutron scattering to reveal that the dilute antiferromagnet Mn(0.35)Zn(0.65)F2 exhibits stable long-range antiferromagnetic order alongside short-range nonequilibrium clusters below the glassy temperature, with critical behavior matching the random-exchange Ising model.

Contribution

It provides detailed neutron scattering evidence of coexistence of long-range order and short-range clusters in a highly diluted antiferromagnet, extending understanding of its critical behavior.

Findings

Stable antiferromagnetic long-range order below T_N

Unusual scattering behavior below T_g indicating short-range clusters

Critical exponents consistent with the random-exchange Ising model

Abstract

The highly diluted antiferromagnet Mn(0.35)Zn(0.65)F2 has been investigated by neutron scattering in zero field. The Bragg peaks observed below the Neel temperature TN (approximately 10.9 K) indicate stable antiferromagnetic long-range ordering at low temperature. The critical behavior is governed by random-exchange Ising model critical exponents (nu approximately 0.69 and gamma approximately 1.31), as reported for Mn(x)Zn(1-x)F2 with higher x and for the isostructural compound Fe(x)Zn(1-x)F2. However, in addition to the Bragg peaks, unusual scattering behavior appears for |q|>0 below a glassy temperature Tg approximately 7.0 K. The glassy region T<Tg corresponds to that of noticeable frequency dependence in earlier zero-field ac susceptibility measurements on this sample. These results indicate that long-range order coexists with short-range nonequilibrium clusters in this highly diluted magnet.