Quantum critical point in the itinerant ferromagnet Ni${}_{1-x}$Rh${}_x$

Abstract

We report a chemical substitution-induced ferromagnetic quantum critical point in polycrystalline Ni${}_{1-x}$Rh${}_x$ alloys. Through magnetization and muon spin relaxation measurements, we show that the ferromagnetic ordering temperature is suppressed continuously to zero at $x_{crit}=0.375$ while the magnetic volume fraction remains 100% up to $x_{crit}$, pointing to a second order transition. Non-Fermi liquid behavior is observed close to $x_{crit}$, where the electronic specific heat $C_{el}/T$ diverges logarithmically, while immediately above $x_{crit}$ the volume thermal expansion coefficient ${\alpha }_V/T$ and the Grüneisen ratio $\Gamma ={\alpha }_V/C_{el}$ both diverge logarithmically in the low temperature limit, further indication of a ferromagnetic quantum critical point in Ni${}_{1-x}$Rh${}_x$.

15 pages, 4 figures