Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 21: Magnetic Materials

MA 21.4: Talk

Wednesday, March 24, 2010, 16:00–16:15, H23

Interplay between chemical and magnetic orders in alloys — •Josef Kudrnovsky¹, Vaclav Drchal¹, and Ilja Turek² — ¹Institute of Physics AS CR, Prague — ²Institute of Physics of Materials AS CR, Brno

Based on the first-principles modeling we will investigate the interplay between the chemical and magnetic orders in the magnetic transition metal alloys. As a case study we will investigate the change of magnetic order due to the chemical order-disorder transformation in fcc-Ni(75)Fe(25), fcc-Ni(75)Mn(25), and bcc-Fe(50)Al(50). The theoretical modeling is done in two steps: in the first-step we will determine the electronic structure of studied magnetic alloys in both disordered and ordered state (Cu3Au-structure for fcc NiFe and NiMn alloys, CsCl-structure for bcc FeAl alloys) by using the tight-binding linear muffin-tin orbital method suitable for description of transition-metal alloys. The chemical disorder is treated in the framework of the coherent-potential approximation. In the second step, the calculated electronic structure is used to estimate the pair exchange interactions by using the method of infinitesimal rotations (the construction of the classical Heisenberg model) for ordered and disordered phases. We will demonstrate that chemical ordering strongly influences the magnetic order in fcc-NiMn and bcc-FeAl alloys. This can be understood on the basis of calculated exchange Heisenberg parameters of alloys in both ordered and disordered phases.