The Emergence of an Itinerant Ferromagnetic State in Co‐Doped YNi5: A Critical Behavior Study of the Phase Transition

Abstract

YNi5 is an enhanced Pauli paramagnetic material, and this work is devoted to the effect of Co doping at the Ni site of YNi5. It is found that at 10% Co doping, the sample turns ferromagnetic, with a weak itinerant character. The critical behaviours of the 10% Co‐doped sample (i.e., YNi4.5CO0.5) in its polycrystalline form are examined through bulk magnetization measurements. The second‐order phase transition from the paramagnetic to the ferromagnetic state is confirmed by the positive slope of the Arrott plots. To obtain the most reliable values of the critical exponents, an extensive analysis of the magnetization data is performed, which includes a modified Arrott plot, Kouvel–Fisher plot, and critical isotherm analysis. The best values of the exponent obtained are β = 0.179 (±0.002), γ = 1.429 (±0.002), and TC = 9.1 K. These values are close to a 2D Ising model along with the long‐range exchange decaying as J(r) ≈ r−(3.6). It is found that this extended exchange is a typical characteristic of many itinerant ferromagnets, whereas the 2D nature is likely to be connected with the layered crystal structure.