Magnetic refrigeration capabilities of magnetocaloric Ni2Mn:75Cu:25Ga

Doping-driven competition between energetically similar ground states leads to many exciting materials phenomena such as the emergence of high-\emph{T$_{c}$} superconductivity, diluted magnetic semiconductors, and colossal magnetoresistance. Doped Ni$_{2}$MnGa Heusler alloy, which is a multifunctional ferromagnetic alloy with various exotic physical properties demonstrates this notion of rich phenomenology \emph{via} modified ground spin states. Adopting this generic concept, here we will present a novel doped Ni$_{2}$Mn$_{.75}$Cu$_{.25}$Ga alloy that offers unprecedented co-existence of the magnetocaloric effect and fully controlled ferromagnetism at room temperature. Application of site engineering enables us to manipulate the ground spin state that leads to the decrease in magnetic transition temperature and also increases the delocalization of the Mn magnetism. SQUID magnetometery suggests that Cu doping enhances the saturation magnetization, coercive field and clarity of magnetic hysteresis loops. By exploiting x-ray absorption techniques and measuring element specific magnetic hysteresis loops, here we will describe the microscopic origin of enhnaced magnetocaloric properties and \emph{d-d} interaction driven charge transfer effects in Ni$_{2}$Mn$_{.75}$Cu$_{.25}$Ga