|Name||Mr. Dallas Mann|
EVOLUTION FROM PARAMAGNETISM TO FERROMAGNETISM IN Ni3–xCoxB GUIDED BY ELECTRONIC STRUCTURE ANALYSIS
Dallas K. Mann, Mykola Abramchuk, and Michael Shatruk
Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, United States
In recent years, the rapid advancement of magnetic refrigeration technology, caused by the discovery of the giant magnetocaloric effect (MCE) around room temperature,1 has led to the expansion of research efforts on itinerant magnets, which are believed to be the most promising group of magnetocaloric materials for practical implementation.2 The MCE is caused by application and removal of an external magnetic field, which allows to harvest the changes in the magnetic and lattice entropy of a material and achieve a cooling effect analogous to that seen in the conventional gas refrigeration technology. Our group has earlier demonstrated that electronic structure calculations can serve as a powerful method for the prediction of itinerant ferromagnetic behavior in intermetallic compounds.3 In this vein, we found that the Ni3–xCoxB was promising, because the substitution of cobalt for nickel atoms should shift the Fermi level to a high peak in the electronic density of states (DOS). At some level of doping, the Stoner criterion for itinerant ferromagnetism should be satisfied. To test this prediction, we prepared a series of Ni3–xCoxB samples and investigated the evolution of their magnetic behavior with the Co content. Indeed, we found that materials with x ≥ 1 exhibit ferromagnetic phase transition with the ordering temperature gradually increasing for Co-richer samples. The synthesis, structural changes, and magnetic ordering observed for this series of materials will be discussed in the presentation.