Ferromagnetic quantum critical point induced by dimer-breaking in SrCo 2 (Ge 1-x P x ) 2

Abstract

In contrast to classical phase transitions driven by temperature,a quantum critical point (QCP) defines a transition at zero temperature that is driven by non-thermal parameters 1-3 . In the known quantum critical d-electron systems, tuning the electronic bandwidth by means of changing the applied pressure or unit-cell dimensions, or tuning the d-state population, is used to drive the criticality 4-6 . Here we describe how a novel chemical parameter, the breaking of bonds in Geg-Ge dimers that occurs within the intermetallic framework in SrCo 2 (Ge 1-x P x ) 2 , results in the appearance of a ferromagnetic (FM) QCP. Although both SrCo 2 P 2 and SrCo 2 Ge 2 are paramagnetic, weak itinerant ferromagnetism unexpectedly develops during the course of the dimer breaking, and a QCP is observed at the onset of the FM phase. The use of chemical bond breaking as a tuning parameter to induce QCP opens an avenue for designing and studying novel magnetic materials. © 2011 Macmillan Publishers Limited. All rights reserved.