Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 30: Magnetic Materials II
MA 30.3: Vortrag
Mittwoch, 18. März 2015, 15:30–15:45, H 0112
Effect of annealing on the magnetic state in Ni-doped FeRh alloys — •Alisa Chirkova1, 2, 3, Alexander Funk1, Anja Waske1, Konstantin Nenkov1, Ludwig Schultz1, Nikolai Baranov2, 3, and Thomas George Woodcock1 — 1IFW Dresden, Dresden, Germany — 2Institute of Metal Physics, Yekaterinburg — 3Ural Federal University, Yekaterinburg
FeRh alloys are known for the antiferromagnetic (AF) - ferromagnetic (FM) phase transition which takes place at about 360 K on heating; the crystal symmetry of CsCl-type (α ′ ) is retained. The transition temperature Tt can be changed by additions of other d-metals [1]; Ni shifts Tt down to about 150 K and at 2 at. % Ni only the FM state exists. Hydrostatic pressure raises Tt and in Ni-doped samples the effect is stronger. Depending on the cooling rate after long term annealing, either AF or FM states were produced in (Fe0.965Ni0.035)49Rh51 samples at 2 K. Quenching produced the AF state, whereas cooling at 1 K/min resulted in the FM state. Microstructural analysis revealed the presence of retained high temperature γ phase. The γ phase is paramagnetic, Rh-rich (60 at.%) and contains twice as much Ni as α ′ . The quenched (AF) sample has 0.070 volume fraction of the γ phase against 0.035 in the slow-cooled (FM) sample which indicates that Ni content of the α ′ phase differs between the samples, thus explaining the different magnetic state. The possible additional effect of strain on the phase boundaries will also be considered.
[1] N.V. Baranov, E.A. Barabanova, J. Alloys Compd. 219 (1995) 139.