# Magnetic materials at finite temperatures: thermodynamics and combined spin and molecular dynamics derived from first principles calculations

## Abstract

We present a unified approach to describe the combined behavior of the atomic and magnetic degrees of freedom in magnetic materials. Using Monte Carlo simulations directly combined with first principles the Curie temperature can be obtained ab initio in good agreement with experimental values. The large scale constrained first principles calculations have been used to construct effective potentials for both the atomic and magnetic degrees of freedom that allow the unified study of influence of phonon-magnon coupling on the thermodynamics and dynamics of magnetic systems. The MC calculations predict the specific heat of iron in near perfect agreement with experimental results from 300K to above Tc and allow the identification of the importance of the magnon-phonon interaction at the phase-transition. Further Molecular Dynamics and Spin Dynamics calculations elucidate the dynamics of this coupling and open the potential for quantitative and predictive descriptions of dynamic structure factors in magnetic materials using first principles-derived simulations.

- Authors:

- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Univ. of Georgia, Athens, GA (United States). Center for Simulational Physics
- Univ. of North Carolina, Asheville, NC (United States). Dept. of Physics
- Univ. of Tennessee, Knoxville, TN (United States). National Inst. for Computational Sciences
- Florida State Univ., Tallahassee, FL (United States). Dept. of Physics

- Publication Date:

- Research Org.:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF) and Center for Defect Physics (CDP)

- Sponsoring Org.:
- USDOE Office of Science (SC)

- OSTI Identifier:
- 1222549

- DOE Contract Number:
- AC05-00OR22725

- Resource Type:
- Conference

- Resource Relation:
- Conference: XXVI IUPAP Conference on Computational Physics, CCP2014, Boston, MA (United States), 11-14 Aug 2014

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 36 MATERIALS SCIENCE; MAGNETIC MATERIALS; COMPUTERIZED SIMULATION; MOLECULAR DYNAMICS METHOD; SPIN; CURIE POINT; IRON; PHONONS; SPECIFIC HEAT; DEGREES OF FREEDOM; MONTE CARLO METHOD; THERMODYNAMICS; STRUCTURE FACTORS; MAGNONS; COUPLING; POTENTIALS; PHASE TRANSFORMATIONS; INTERACTIONS

### Citation Formats

```
Eisenbach, Markus, Perera, Meewanage Dilina N., Landau, David P, Nicholson, Don M., Yin, Junqi, and Brown, Greg.
```*Magnetic materials at finite temperatures: thermodynamics and combined spin and molecular dynamics derived from first principles calculations*. United States: N. p., 2015.
Web.

```
Eisenbach, Markus, Perera, Meewanage Dilina N., Landau, David P, Nicholson, Don M., Yin, Junqi, & Brown, Greg.
```*Magnetic materials at finite temperatures: thermodynamics and combined spin and molecular dynamics derived from first principles calculations*. United States.

```
Eisenbach, Markus, Perera, Meewanage Dilina N., Landau, David P, Nicholson, Don M., Yin, Junqi, and Brown, Greg. Thu .
"Magnetic materials at finite temperatures: thermodynamics and combined spin and molecular dynamics derived from first principles calculations". United States.
doi:. https://www.osti.gov/servlets/purl/1222549.
```

```
@article{osti_1222549,
```

title = {Magnetic materials at finite temperatures: thermodynamics and combined spin and molecular dynamics derived from first principles calculations},

author = {Eisenbach, Markus and Perera, Meewanage Dilina N. and Landau, David P and Nicholson, Don M. and Yin, Junqi and Brown, Greg},

abstractNote = {We present a unified approach to describe the combined behavior of the atomic and magnetic degrees of freedom in magnetic materials. Using Monte Carlo simulations directly combined with first principles the Curie temperature can be obtained ab initio in good agreement with experimental values. The large scale constrained first principles calculations have been used to construct effective potentials for both the atomic and magnetic degrees of freedom that allow the unified study of influence of phonon-magnon coupling on the thermodynamics and dynamics of magnetic systems. The MC calculations predict the specific heat of iron in near perfect agreement with experimental results from 300K to above Tc and allow the identification of the importance of the magnon-phonon interaction at the phase-transition. Further Molecular Dynamics and Spin Dynamics calculations elucidate the dynamics of this coupling and open the potential for quantitative and predictive descriptions of dynamic structure factors in magnetic materials using first principles-derived simulations.},

doi = {},

journal = {},

number = ,

volume = ,

place = {United States},

year = {Thu Jan 01 00:00:00 EST 2015},

month = {Thu Jan 01 00:00:00 EST 2015}

}