Magnetic field dependence of magnetic correlations in a pyrochlore Heisenberg antiferromagnet

Recent neutron experiments on the S=1 pyrochlore NaCaNi₂F₇ [1] revealed a dynamic structure factor exhibiting pinch points and a continuum of high energy magnetic excitations. These signatures point towards a magnetic ground-state which can be described by an almost ideal Heisenberg antiferromagnet on the pyrochlore lattice. Although a highly degenerate ground state its expected at low temperatures, disorder freezes the spin degrees of freedom so that a specific spin configuration is preferred [2]. How disorder induces a frozen spin state in this Coulomb phase [3] remains to be fully understood. We present here a set of neutron scattering measurements in NaCaNi₂F₇ as a function of external magnetic field. Above a threshold field, H > 2 T, a long-range ordered magnetic field polarized phase emerges. I will discuss the magnetic field and temperature evolution of magnetic correlations in NaCaNi₂F₇ through this polarized phase.

[1] Krizan, J. W. and Cava, R. J., Physical Review B 92, 014406 (2015)
[2] Plumb, K. W. et al, Nat. Phys. 1, 54 (2019)
[3] Henley, C. L., Annu. Rev. Condens. Matter Phys 1, 179 (2010)