Evidence of weak itinerant ferromagnetism and Griffiths like phase in MnFeGe

Abstract

Realizing the itinerant type of magnetic exchange in Mn-based alloys is quite unusual because of the weak hybridization between Mn-moments and conduction electrons. However, in the current study, we found MnFeGe to exhibit weak itinerant type magnetic character possibly arising due to the hybridization between Mn, Fe atoms with Ge atoms. Here, we present a comprehensive structural and magnetic study on polycrystalline MnFeGe. Rietveld refinement of the XRD pattern confirms that Mn and Fe atoms randomly (atomic disorder) occupy the 2a and 2d sites in MnFeGe. From the magnetic measurements, Curie temperature and saturation moment values are found to be 162 K and 1.58 at 2 K, respectively. The relative low values of Curie temperature, saturation magnetic moment, and a large value of Rhodes–Wohlfarth ratio (∼3.4) indicate the weak itinerant ferromagnetic character of the system. The Takahashi spin fluctuation theory analysis further supports the weak itinerant ferromagnetism in MnFeGe. Besides, we also observed Griffiths phase (GP) like behavior above the Curie temperature, which is attributed to the presence of atomic disorder in the system. The presence of GP is further confirmed by the zero spontaneous magnetization. Our findings demonstrate that MnFeGe is one of the very few Mn-based systems with weak itinerant magnetic behavior.