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Information × Registration Number 0211U006691, 0109U006361 , R & D reports Title Induced external influences (electric and magnetic fields, pressure, temperature) phase transformations into alloys of transitive metals. popup.stage_title Head Valkov Victor Ivanovich, Registration Date 10-03-2011 Organization Donetsk Institute of Physics @ Engineering named after O.O.Galkin NAS of Ukraine popup.description2 On the third stage of research work the study of iron-manganese pnictides Mn(2- x)Fe(x)P0.5As0.5 is continued with the purpose of verification of possibility of improvement of their functional magnetocaloric descriptions due to the change of cation composition, and, consequently, electronic structure and properties of material related to it. The results of research of magnetic and magnetocaloric properties of the indicated alloys (0<x<0,5) are presented in the magnetic fields to 8Т in the wide interval of temperatures (4,2<Т<700К). From the isotherms of magnetizing, temperatures of spontaneous origin of the ferromagnetic state taken off near-by, the changes of entropy are certain at the change of magnetic-field from 0 to 2, 4, 5, 8Т and dependences are built. The monotonous decline of temperatures of magnetic phase transitions is set disorder-order and order-order with the height of concentration of manganese and complete suppression of ferromagnetic phase in Mn1.5Fe0.5P0.5As0.5. Extreme character of concentration dependences of maximal jump of entropy (and corresponding cold capacity) and size of ferromagnetic moment of elementary cell is educed with maximums at x=0,9 and x=0,8 accordingly. Finding is compared to expected from the first principles by the method of KKR-CPA by the sizes of ferromagnetic moments - divergence at 0,5<x<0,7 contacts with appearance of antiferromagnetic component of magnetic structure. In conclusion drawn reasoning about perspective of alloys of Mn(2-x)Fe(x)P0.5As0.5 for the use in magnetic refrigerators which work at the area of room temperature. Research of change of size of local magnetic moments of ML is conducted in MnAs under the action of pressure by means of empiric method, that allows rectifying such changes by the analysis of magnetovolume effects. It is got, that at the decline of temperature of magnetоstructural phase transition of first order from ferromagnetic FM(B81) in the paramagnetic state of PM(B31) the saltatory diminishing of size of ML grows, so that the smooth change of the magnetic state of atoms of Mn takes place in the paramagnetic area of the phase P -Т- diagram (near-by a border with the phase of FM(B81)) from a "high-spin" with ML = 3.2µB at ТС = 318 K to "low-spin" with ML = 2.2µB at ТС = 225К. At the further decline of temperature and passing to the area of existence of double spiral structure of DS(B31) the low-spin state of atoms of Mn is attained near-by the indicated border saved (ML = 2.1µB at ТK = 10 K). The increase of pressure in the phase of В31 at subzero temperatures results in the smooth diminishing of size of local magnetic moments of atoms of Mn in the " low-spin " state to the value ML = 1.48µB at P = 38 kbar. Comparison of the got results is done with present literary data. Product Description popup.authors Варюхін Дмитро Вікторович Головчан Олексій Віталійович Грибанов Ігор Федорович Дворніков Євген Олександрович Каменєв Віктор Іванович Сіваченко Олександр Павлович Таренков Володимир Юрійович Тодрис Боріс Михайлович popup.nrat_date 2020-04-02 Close