Quantum Griffiths Phase in the Weak Itinerant Ferromagnetic Alloy Ni_1-xV_x

Sara Ubaid-Kassis
Thomas Vojta, Missouri University of Science and Technology
Almut Schroeder

This document has been relocated to http://scholarsmine.mst.edu/phys_facwork/383

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Abstract

We present magnetization (M) data of the d-metal alloy Ni_1-xV_x at vanadium concentrations close to x_x ~ 11.4% where the onset of long-range ferromagnetic (FM) order is suppressed to zero temperature. Above x_c, the temperature (T) and magnetic field (H) dependencies of the magnetization are best described by simple nonuniversal power laws. the exponents of M/H ~ T ^γ and M ~ H^α are related by 1-γ=α for wide temperature (10c to γ<0.1 for x=15%. This behavior is not compatible with either classical or quantum critical behavior in a clean 3D FM. Instead it closely follows the predictions for a quantum Griffiths phase associated with a quantum phase transition in a disordered metal. Deviations at the lowest temperatures hint at a freezing of large clusters and the onset of a cluster glass phase.