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In-Plane Thermal Conductivity of N d 2 C u O 4 : Evidence for Magnon Heat Transport

2003; American Physical Society; Volume: 91; Issue: 14 Linguagem: Inglês

10.1103/physrevlett.91.146601

1092-0145

Rongying Jin, Y. Onose, Y. Tokura, David Mandrus, Pengcheng Dai, B. C. Sales,

High-pressure geophysics and materials

We report the temperature and magnetic field dependence of the in-plane thermal conductivity (${\ensuremath{\kappa}}_{ab}$) of high-quality monocrystalline ${\mathrm{N}\mathrm{d}}_{2}{\mathrm{C}\mathrm{u}\mathrm{O}}_{4}$. Isothermal measurements of the field dependence of ${\ensuremath{\kappa}}_{ab}$ at low temperatures ($2\text{ }\text{ }\mathrm{K}\ensuremath{\le}T\ensuremath{\le}5\text{ }\text{ }\mathrm{K}$) show no change in ${\ensuremath{\kappa}}_{ab}$ below a critical magnetic field ${H}_{c}$ (${H}_{c}\ensuremath{\approx}4.5\text{ }\text{ }\mathrm{T}$ for $H\ensuremath{\parallel}[100]$) and ${H}_{c}\ensuremath{\approx}2.5\text{ }\text{ }\mathrm{T}$ for $H\ensuremath{\approx}\ensuremath{\parallel}[110]$). Above ${H}_{c}$, ${\ensuremath{\kappa}}_{ab}$ more than doubles as $H$ is increased to 9 T. At ${H}_{c}$, there is a transition from a noncollinear to a collinear arrangement of the Nd and Cu spins and a collapse of the gap, $\ensuremath{\Delta}$, in an acoustic magnon branch at $\mathbf{k}=0$. Closure of this gap appears to allow the conduction of substantial amounts of heat by acoustic magnons.