Journal Article

FZJ-2025-01797

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Paramagnetic fluctuations of the magnetocaloric compound MnFe 4 Si 3

Biniskos, N. (Corresponding author)FZJ* ; Schmalzl, K.FZJ* ; Persson, J.FZJ* ; Raymond, S.

2025
Inst. Woodbury, NY

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Please use a persistent id in citations: doi:10.1103/PhysRevB.111.054424  doi:10.34734/FZJ-2025-01797

Abstract: An inelastic neutron scattering technique is employed to investigate the paramagnetic spin dynamics in a single-crystalline sample of the magnetocaloric compound MnFe4Si3. In the investigated temperature range, 1.033 x TC to 1.5 x TC , where TC is the Curie temperature, the spin fluctuations are well described by the ferromagnetic Heisenberg model predictions. Apart from the Heisenberg exchange, additional pseudodipolar interactions manifest through a finite long-wavelength relaxation rate that vanishes at the transition temperature (TC = 305 K). Based on the characteristic extent of spin fluctuations in wave-vector and energy space, we determine that the nature of magnetism in MnFe4Si3 is localized above room temperature. This contrasts with the most celebrated Mn- and Fe-based magnetocaloric materials that are considered as itinerant magnets. The field dependence of the paramagnetic spectra shows a strong suppression of the quasielastic excitations, while a field-induced spin-wave mode appears at finite-energy transfers for a magnetic field of 2 T. This modification of the spectra suggests a decrease of magnetic entropy with applied magnetic field that finds echo in the magnetocaloric properties of the system.

Keyword(s): Magnetic Materials (1st) ; Condensed Matter Physics (2nd) ; Magnetism (2nd)

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Contributing Institute(s):

1. Streumethoden (JCNS-2)
2. JARA-FIT (JARA-FIT)
3. JCNS-ILL (JCNS-ILL)
4. JCNS-FRM-II (JCNS-FRM-II)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. 6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ) (POF4-6G4) (POF4-6G4)

Experiment(s):

1. ILL-IN12: Cold neutron 3-axis spectrometer

Appears in the scientific report 2025

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Electronics and Telecommunications Collection ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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