First-order magnetostructural transition in Ni-Mn-Sn powder - A matter of particle and grain size
Abstract
In Ni-Mn-based Heusler alloys, the magnetocaloric effect originates from a first-order magnetostructural transition (FOMST). However, the influence of particle and grain size on thermal hysteresis, transition width, and nucleation and growth mechanism remains poorly understood, as mechanical grinding can introduce residual stresses and processing-induced defects. In this study, we examined the size dependence of the FOMST in gas-atomized Ni-Mn-Sn powder by combining microstructural characterization with temperature-dependent XRD, magnetometry, calorimetry and single-particle measurements, enabling decoupling of size dependence from processing-related influences. We observed a pronounced size dependence of the transition ranges (Ms-Mf) and (Af-As), which decrease with decreasing particle size and approach zero for single-crystalline particles below ~20-30 micrometer. The thermal hysteresis decreases with increasing particle size, reaching a lower limit of 17 K for large polycrystalline particles above 100 micrometer. EBSD reveals a nearly constant grain size, implying a transition from polycrystalline to single-crystalline particles as particle size decreases. In polycrystalline particles, multiple grains transform gradually over an extended temperature interval because grain boundaries act as barriers to the progression of transformation. In contrast, single-grain particles lack preferred nucleation sites, resulting in larger hysteresis, while the absence of barriers to transformation propagation causes the entire particle to transform in a narrow range. These results demonstrate that the size dependence of the FOMST is governed by the interplay between particle size, grain boundaries, and the free particle surface.
Related
- High Energy Neutrinos, Gravitational Waves, and Dark Matter from a Cosmological First Order Phase Transition
- Two-Component Dark Matter and Strongly First-Order Electroweak Phase Transition via a Two-Step Mechanism in the Inert Doublet plus Real Singlet Model
- Strong First-Order Electroweak Phase Transition and Gravitational Waves in a ℤ4 Fermion-Scalar Dark Matter Model
- Particle Inertia-Driven Pore Formation over Material Property Effects in Laser Powder-blown Directed Energy Deposition
- The devil in the transition: NLO nucleation and the particle physics behind the PTA signal
BibTeX
@misc{puy2026firstorder,
title = {{First-order magnetostructural transition in Ni-Mn-Sn powder - A matter of particle and grain size}},
author = {Johannes Puy and David Koch and Enrico Bruder and Sagar Ghorai and Benedikt Beckmann and Heiner Gutte and Volodymyr Baran and Oliver Gutfleisch and Franziska Scheibel},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.33556},
eprint = {2610.33556},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.33556},
note = {CC BY-SA 4.0},
}
RIS
TY - UNPB
TI - First-order magnetostructural transition in Ni-Mn-Sn powder - A matter of particle and grain size
AU - Johannes Puy
AU - David Koch
AU - Enrico Bruder
AU - Sagar Ghorai
AU - Benedikt Beckmann
AU - Heiner Gutte
AU - Volodymyr Baran
AU - Oliver Gutfleisch
AU - Franziska Scheibel
PY - 2026
DA - 2026/10/24
PB - arXiv
DO - 10.48550/arxiv.2610.33556
UR - https://arxiv.org/abs/2610.33556
AB - In Ni-Mn-based Heusler alloys, the magnetocaloric effect originates from a first-order magnetostructural transition (FOMST). However, the influence of particle and grain size on thermal hysteresis, transition width, and nucleation and growth mechanism remains poorly understood, as mechanical grinding can introduce residual stresses and processing-induced defects. In this study, we examined the size dependence of the FOMST in gas-atomized Ni-Mn-Sn powder by combining microstructural characterization with temperature-dependent XRD, magnetometry, calorimetry and single-particle measurements, enabling decoupling of size dependence from processing-related influences. We observed a pronounced size dependence of the transition ranges (Ms-Mf) and (Af-As), which decrease with decreasing particle size and approach zero for single-crystalline particles below ~20-30 micrometer. The thermal hysteresis decreases with increasing particle size, reaching a lower limit of 17 K for large polycrystalline particles above 100 micrometer. EBSD reveals a nearly constant grain size, implying a transition from polycrystalline to single-crystalline particles as particle size decreases. In polycrystalline particles, multiple grains transform gradually over an extended temperature interval because grain boundaries act as barriers to the progression of transformation. In contrast, single-grain particles lack preferred nucleation sites, resulting in larger hysteresis, while the absence of barriers to transformation propagation causes the entire particle to transform in a narrow range. These results demonstrate that the size dependence of the FOMST is governed by the interplay between particle size, grain boundaries, and the free particle surface.
ER -