Magnetic and structural properties of Lu2(Fe, Mn)17Hy hydrides
The Lu2Fe17−xMnxHy, x = 0–2, y = 0–3, hydrides with the Th2Ni17-type crystal structure were prepared and their structural and magnetic parameters were studied. The lattice parameters measured at room temperature increase smoothly with H content. The magnetic measurements indicate that the Lu2Fe17Hy hydrides (with y up to 1.77) are antiferromagnets at high temperatures and ferromagnets at low temperatures. The Lu2Fe16.5Mn0.5 compound also has a high temperature antiferromagnetic state, but its hydrides are ferromagnets only. The Lu2Fe17−xMnxHy hydrides, with x = 0.7 and 2, are ferromagnets with Tc monotonically increasing with H content. The saturation magnetization measured for Lu2Fe17−xMnxHy, (x = 0,0.5,0.7,2 and 0
Changes in magnetic state of Y2(Fe,Mn)17-H systems: Regularities and potentialities
Abstract A systematic study is made of the magnetic properties of the hydrides of Y2Fe17−xMnxHy intermetallic alloys (0 ⩽ x ⩽ 8 and 0 ⩽ y ⩽ 4.4 at.H/f.u.) and the exchange interaction parameters of these compounds are estimated. It is found that hydrogen atoms enhance the ferromagnetic interactions. The decrease of the Curie temperature observed in both hydrides and parent alloys with substitution of manganese for iron gives an indication of the reinforcement of negative exchange interactions. As a result the magnetic order of the compounds under study is subject to change at high (x > 6) manganese concentration. The transformation of magnetic state in the Y2Fe17−xMnx-H system is explained on the basis of molecular field theory connecting the Curie temperatures with the value and sign of exchange interaction integrals (AFeFe, AMnMn, and AFeMn) for magnetoactive atoms: iron and manganese.
ROOM- AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF Sm(CobalFexCu0.088Zr0.025)7.5 (x=0.30) SINTERED MAGNETS
The effect of Fe content on room- and high-temperature magnetic properties of Sm(CobalFexCu0.088Zr0.025)7.5 (x=0-0.30) sintered magnets, prepared by the conventional powder metallurgy method, has been systematically studied. With increasing Fe content, the remanences BT and maximum energy products (BH)max at room temperature gradually increase and reach optimal values of 1.055 T with x=0.27 for BT, and 205 kJ/m3 with x=0.21 for (BH)max, respectively, and then drop sharply with further Fe increase. An excessive addition of Fe (x≥0.24) results in rapid deterioration of permanent magnetic properties due to the formation of a considerable amount of FeCo soft magnetic phase. It was found that the effect of Fe content on high temperature stability is huge. The lower the Fe content, the smaller the temperature coefficient of coercivity. When x=0.07, a temperature coefficient of coercivity of -0.14%/K (293-723 K) can be achieved, as compared with -0.23%/K for x=0.21. BT of 0.725 T, bHc of 517 kA/m, iHc of 764 kA/m, and (BH)max of 95 kJ/m3 at 723 K were obtained, and the B-H demagnetization curve remains a straight line.