# David Wagenknecht: Alloy analogy model: An efficient treatment of finite temperatures from the first principles

**Date:**Wednesday, 12 December 2018 14:10 - 15:10

**Venue:** lecture room F2, first floor, Ke Karlovu 5 - Prague 2

We have a pleasure to invite you to attend the joint seminar

of the Department of Condensed Matter Physics (DCMP)

and the Materials Growth and Measurement Laboratory (MGML) https://mgml.eu.

Program

Alloy analogy model: An efficient treatment of finite temperatures from the first principles

lecture given by:

**David Wagenknecht**

*Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University Ke Karlovu 5, CZ-121 16, Prague, Czech Republic*

The seminar takes place in the lecture room F2

of the Faculty of Mathematics and Physics, Ke Karlovu 5, Praha 2

on Wednesday, 5.12. 2018 from 14:10

Vladimír Sechovský

On behalf of the DCMP and MGML

**Abstract **

Ab initio calculations with a temperature-induced phenomena (phonons and magnons) represent a challenging task, especially because of numerical expenses. The alloy analogy model (AAM) is an approach that uses a similarity of disordered solids with random alloys and it leads to an efficient description of finite temperatures.

First-principles calculations with combined influence of chemical disorder, atomic displacements (phonons), and magnetic fluctuations (magnons) based on the AAM will be presented. The framework within the fully relativistic tight-binding linear muffin-tin orbital (TB-LMTO) method and the coherent potential approximation (CPA) gave an agreement with experimental data for transition metals and simple alloys [1, 2]. It was also successfully used to describe extreme conditions in the Earth's core where the effect of spin disorder plays an important role [3].

The most complex system studied by the AAM so far is half-metallic half-Heusler NiMnSb [4]. Although it has four sublattices, it may influenced by many chemical defects, and strong Mn magnetic moments must be taken into account, temperature-dependent calculations agree perfectly with experimental longitudinal resistivities and the anomalous Hall effect. Experimentally hardly accessible spin polarization of the electrical current P > 90% is obtained even at room temperature which makes NiMnSb an ideal candidate for a construction of novel spintronic devices.

[1] D. Wagenknecht et al. T-MAG 53 11 (2017)

[2] D. Wagenknecht et al. Proc. SPIE 10357, 103572W (2017)

[3] V. Drchal et al. PRB 96, 024432 (2017)

[4] D. Wagenknecht et al. JMMM (2018): In press, DOI: 10.1016/j.jmmm.2018.11.047

David Wagenknecht

### Map

### All Dates

- Wednesday, 12 December 2018 14:10 - 15:10