Phase transitions and magnetocaloric effects in intermetallic compounds MnFeX(X=P,As,Si,Ge)

Since the discovery of giant magnetocaloric effect in MnFeP1-x As x compounds,much valuable work has been performed to develop and improve Fe2P-type transition-metal-based magnetic refrigerants.In this article,the recent progress of our studies on fundamental aspects of theoretical considerations and experimental techniques,effects of atomic substitution on the magnetism and magnetocalorics of Fe2P-type intermetallic compounds MnFeX（X=P,As,Ge,Si） is reviewed.Substituting Si（or Ge） for As leads to an As-free new magnetic material MnFeP1-xSi（Ge）x.These new materials show large magnetocaloric effects resembling MnFe（P,As） near room temperature.Some new physical phenomena,such as huge thermal hysteresis and ＇virgin＇ effect,were found in new materials.On the basis of Landau theory,a theoretical model was developed for studying the mechanism of phase transition in these materials.Our studies reveal that MnFe（P,Si） compound is a very promising material for room-temperature magnetic refrigeration and thermo-magnetic power generation.

Thermo-chemical conversion of coal samples under high temperature

Exhaustion of profitable coal resources makes for need of innovation including underground coal gasification(UCG).One of the most important problems of UCG is evaluation of the combustion area in underground coal seams.Physicochemical parameters of coal,in a whole,and coal mineral substance are changed under heating and combusting.Thermo-chemical conversion of coal mineral components has an effect on magnetic characteristics of coal seam and can be used for real-time control of combusting area.To this guessing check laboratory experiments have been made as an activity of the Far Eastern Federal University.Our investigation based on a theoretical analysis and laboratory simulation tests.Typical results of the laboratory experiments are presented below.Under heating coal thermo-chemical magnetization is forming.Coal's magnetic parameters varieties from anti-ferromagnetiсto ferromagnetic.Anti-ferromagnetic pyrite and siderite presented into coal mass is transformed into magnetic hematite and magnetite under heating.Therefore,geomagnetic is expected to be a useful geophysical tool to for evaluation of combustion volume and its migration for underground coal gasification.

Study of the Thermo-magnetic Effect of Gd-Tb Alloys at Near Room Temperature

Magnetic refrigeration technique has attracted wide interest because of its high effi-ciency and causing no environment contamination. There is still much essentialwork to do about the magnetic refrigeration technique at near room temperature, e.g.to develop new magnetic refrigerators with high thermo-magnetic effect.In