Special Issue "New Aspects of Ferromagnetic Shape Memory Alloys: From Fabrication to Applications"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Smart Materials".

Deadline for manuscript submissions: 31 July 2021.

Special Issue Editor

Prof. Dr. Pablo Álvarez-Alonso
E-Mail Website
Guest Editor
Physics department, University of Oviedo, Calvo Sotelo, s/n, 33007 Oviedo, Spain
Interests: rapid-quenched materials; shape memory alloys; magnetocaloric effect; elastocaloric effect

Special Issue Information

Dear Colleagues,

Ferromagnetic shape memory alloys are functional materials that exhibit magnetomechanical coupling, the cause of the wide variety of attractive thermal, mechanical, magnetic, electrical, and optical properties. Among their most known behaviors, the magnetically controlled shape memory effect and caloric effects have attracted the largest attention, although researchers continue to delve into other features of these materials, such as novel martensite transformation arrest, exchange bias, and energy-harvesting.

These materials have demonstrated a great versatility in bulk and single-crystal shapes by tailoring the martensitic transformation through intrinsic and extrinsic parameters, as, for example, chemical composition and pressure, respectively; the development of high-temperature magnetic shape memory alloys is one of the largest exponents of this adaptability.

Even so, many efforts have been successfully done to push the functionality of the ferromagnetic shape memory alloys forward by means of new fabrication routes that reduce the dimensionality of these alloys, opening a world of opportunities in fields like biomedical science and micro/nano-electromechanical systems engineering.

Despite of all these achievements, there still exist challenges such as thermal hysteresis, thermal transport management, and brittleness, which constitute the driving force in the field of ferromagnetic shape memory alloys.

This Special Issue aims to bring the latest research in fabrication processes, characterization, modeling, and applications of ferromagnetic shape memory alloys.

The main topics covered include but are not limited to the following:

  • Production of low dimensionality ferromagnetic shape memory alloys;
  • Twin structure;
  • Magnetic field-induced strain;
  • Modelling of martensite transformation and magnetomechanical properties;
  • Caloric effects;
  • High-temperature magnetic shape memory actuation;
  • Energy-harvesting;
  • Biomedical applications.

Prof. Dr. Pablo Álvarez-Alonso
Guest Editor

Manuscript Submission Information

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Keywords

  • martensite transformation
  • rapid quenching
  • thin films
  • nanostructuration
  • magnetic shape memory effect
  • solid-state refrigeration
  • sensors and actuators
  • biocompatibility

Published Papers (3 papers)

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Research

Open AccessArticle
Dependence of the Magnetization Process on the Thickness of Fe70Pd30 Nanostructured Thin Film
Materials 2020, 13(24), 5788; https://doi.org/10.3390/ma13245788 - 18 Dec 2020
Cited by 2 | Viewed by 466
Abstract
Fe–Pd magnetic shape-memory alloys are of major importance for microsystem applications due to their magnetically driven large reversible strains under moderate stresses. In this context, we focus on the synthesis of nanostructured Fe70Pd30 shape-memory alloy antidot array thin films with [...] Read more.
Fe–Pd magnetic shape-memory alloys are of major importance for microsystem applications due to their magnetically driven large reversible strains under moderate stresses. In this context, we focus on the synthesis of nanostructured Fe70Pd30 shape-memory alloy antidot array thin films with different layer thicknesses in the range from 20 nm to 80 nm, deposited onto nanostructured alumina membranes. A significant change in the magnetization process of nanostructured samples was detected by varying the layer thickness. The in-plane coercivity for the antidot array samples increased with decreasing layer thickness, whereas for non-patterned films the coercive field decreased. Anomalous coercivity dependence with temperature was detected for thinner antidot array samples, observing a critical temperature at which the in-plane coercivity behavior changed. A significant reduction in the Curie temperature for antidot samples with thinner layer thicknesses was observed. We attribute these effects to complex magnetization reversal processes and the three-dimensional magnetization profile induced by the nanoholes. These findings could be of major interest in the development of novel magnetic sensors and thermo-magnetic recording patterned media based on template-assisted deposition techniques. Full article
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Open AccessArticle
The Forced Magnetostrictions and Magnetic Properties of Ni2MnX (X = In, Sn) Ferromagnetic Heusler Alloys
Materials 2020, 13(9), 2017; https://doi.org/10.3390/ma13092017 - 25 Apr 2020
Viewed by 652
Abstract
Experimental studies into the forced magnetostriction, magnetization, and temperature dependence of permeability in Ni2MnIn and Ni2MnSn ferromagnetic Heusler alloys were performed according to the spin fluctuation theory of itinerant ferromagnetism proposed by Takahashi. We investigated the magnetic field ( [...] Read more.
Experimental studies into the forced magnetostriction, magnetization, and temperature dependence of permeability in Ni2MnIn and Ni2MnSn ferromagnetic Heusler alloys were performed according to the spin fluctuation theory of itinerant ferromagnetism proposed by Takahashi. We investigated the magnetic field (H) dependence of magnetization (M) at the Curie temperature TC, and at T = 4.2 K, which concerns the ground state of the ferromagnetic state. The M-H result at TC was analyzed by means of the H versus M5 dependence. At 4.2 K, it was investigated by means of an Arrott plot (H/M vs. M2) according to Takahashi’s theory. As for Ni2MnIn and Ni2MnSn, the spin fluctuation parameters in k-space (momentum space, TA) and that in energy space (frequency space, T0) obtained at TC and 4.2 K were almost the same. The average values obtained at TC and 4.2 K were TA = 342 K, T0 = 276 K for Ni2MnIn and TA = 447 K, T0 = 279 K for Ni2MnSn, respectively. The forced magnetostriction at TC was also investigated. The forced linear magnetostriction (ΔL/L) and the forced volume magnetostriction (ΔV/V) were proportional to M4, which followed Takahashi’s theory. We compared the forced volume magnetostriction ΔV/V and mechanical parameter, bulk modulus K. ΔV/V is inversely proportional to K. We also discuss the spin polarization of Ni2MnIn and other magnetic Heusler alloys. The pC/pS of Ni2MnIn was 0.860. This is comparable with that of Co2MnGa, which is a famous half-metallic alloy. Full article
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Open AccessArticle
Optimizing the Caloric Properties of Cu-Doped Ni–Mn–Ga Alloys
Materials 2020, 13(2), 419; https://doi.org/10.3390/ma13020419 - 16 Jan 2020
Cited by 3 | Viewed by 665
Abstract
With the purpose to optimize the functional properties of Heusler alloys for their use in solid-state refrigeration, the characteristics of the martensitic and magnetic transitions undergone by Ni50Mn25−xGa25Cux (x = 3–11) alloys have been [...] Read more.
With the purpose to optimize the functional properties of Heusler alloys for their use in solid-state refrigeration, the characteristics of the martensitic and magnetic transitions undergone by Ni50Mn25−xGa25Cux (x = 3–11) alloys have been studied. The results reveal that, for a Cu content of x = 5.5–7.5, a magnetostructural transition between paramagnetic austenite and ferromagnetic martensite takes place. In such a case, magnetic field and stress act in the same sense, lowering the critical combined fields to induce the transformation; moreover, magnetocaloric and elastocaloric effects are both direct, suggesting the use of combined fields to improve the overall refrigeration capacity of the alloy. Within this range of compositions, the measured transformation entropy is increased owing to the magnetic contribution to entropy, showing a maximum at composition x = 6, in which the magnetization jump at the transformation is the largest of the set. At the same time, the temperature hysteresis of the transformation displays a minimum at x = 6, attributed to the optimal lattice compatibility between austenite and martensite. We show that, among this system, the optimal caloric performance is found for the x = 6 composition, which displays high isothermal entropy changes (−36 J·kg−1·K−1 under 5 T and −8.5 J·kg−1·K−1 under 50 MPa), suitable working temperature (300 K), and low thermal hysteresis (3 K). Full article
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