Current Trends in Magnetocaloric Materials: An FMD Symposium in Honor of Ekkes Brueck: Phase Equilibria and Magnetic Structure of Magnetocaloric Materials
Sponsored by: TMS Functional Materials Division
Program Organizers: Victorino Franco, Universidad de Sevilla; Frank Johnson, Niron Magnetics, Inc.
Monday 2:30 PM
February 24, 2020
Room: Marina Ballroom F
Location: Marriott Marquis Hotel
Session Chair: Luana Caron, Bielefeld University
2:30 PM Cancelled
Ferromagnetic Shape Memory Heuslers: from Bulk to Nano: Franca Albertini1; Francesca Casoli1; Simone Fabbrici1; Milad Takhsha Ghahfarokhi1; Riccardo Cabassi1; Lucia Nasi1; Cecilia Bennati1; Massimo Solzi2; Francesco Cugini2; Paola Tiberto3; Federica Celegato3; 1IMEM-CNR; 2Università di Parma; 3INRIM
Ferromagnetic shape memory Heuslers have constantly shown new emerging properties exploitable in different application fields, including solid state refrigeration. Giant effects can be driven by external fields, i.e. magnetic field, pressure and stress and by their combined application, enabling their multifunctional exploitation. The wide tunability of crystal structure, magnetic interaction, critical temperatures, order and number of transitions is of great interest. In this talk I will present a thorough study of the magnetic, structural and functional (e.g. caloric, magnetomechanical) properties of NiMn-based compounds and discuss their tailoring potential in bulk and nanostructured materials to improve their exploitation in solid state refrigeration and energy-related applications.
3:00 PM Invited
Magnetocaloric Effect in Heusler-type Magnetic Shape Memory Materials: Volodymyr Chernenko1; Victor L´vov2; Eduard Cesari3; Jose Manuel Barandiaran1; 1BCMaterials & University of the Basque Country (UPV/EHU); 2Taras Shevchenko National University of Kyiv, Kyiv, Ukraine; 3Universitat de les Illes Balears, Palma de Mallorca, Spain
Giant magnetocaloric effect (MCE) is observed in the materials exhibiting magnetostructural first order transformation accompanied by a sharp change of magnetic order. The Heusler-type magnetic shape memory alloys (SMAs) represent such kind of materials. They can be tentatively divided into two groups: metamagnetic and ferromagnetic. The metamagnetic SMAs (MetaMSMAs), typically Ni-Mn-X (X=Sn, In, Sb), exhibit inverse giant MCE in the temperature range of martensitic transformation (MT). Ferromagnetic SMAs (FSMAs), prototype is Ni-Mn-Ga, show a giant conventional MCE at MT merged with Curie temperature. Brief overview of the recent experimental results on MCE in both MetaMSMAs and FSMAs will be presented. The emphasis will be given to the results obtained by the adiabatic and heat capacity under magnetic field techniques.The Landau theory of martensitic-type magnetostructural transformations is proposed for the quantitative description of giant MCE and heat capacity in both MetaMSMAs and FSMAs.
3:30 PM Invited
Unprecedented Magnetism, Magneto-crystalline Anisotropy, and Magneto-structural Phase Transformation in Rare Earth Containing Materials: Durga Paudyal1; Renu Choudhary1; 1Ames Laboratory
In rare earth element based materials the alloyed p-block elements provide chemical formation and stability, and control magnetism exhibited by rare earths. We report here an example of how alloyed non-magnetic element pinpointed an enhanced as well as controlled magnetism, magneto-crystalline anisotropy, and phase transformation. One example is R2T (R = rare earth, T = p-block element), in which the R-5d states strongly hybridize with the T-p states exhibiting large exchange splitting in ferromagnetic configuration. This unexpectedly high exchange splitting is the root cause of the sharp para-magnetic to ferromagnetic transition [1]. The Ames Laboratory is operated for the U.S. Department of Energy (DOE) by Iowa State University of Science and Technology under contract No. DE-AC02-07CH11358. This work was supported by the Office of Science of the U.S. DOE, Division of Materials Sciences and Engineering, Office of Basic Energy Sciences.[1] Nature Comm. 9, 2925 (2018)
4:00 PM Break
4:20 PM Invited
The Interplay of Electronic, Magnetic and Lattice Degrees of Freedom in La-Fe-Si-based Magnetocaloric Materials
: Markus Gruner1; 1University of Duisburg, Essen
State-of-the-art magnetocaloric materials like La(Fe1-xSix)13 or FeRh are characterized by an intricate coupling between the electronic structure, magnetism and lattice degrees of freedom, which is responsible for the large entropy change occuring at a first-order metamagnetic transition. Current investigations show that first-principles calculations in the framework of density functional theory (DFT) in combination with element-resolved experimental techniques such as nuclear resonant inelastic X-ray-scattering, X-ray absorption or Mössbauer spectroscopy can resolve the contribution of specific degrees of freedom to the magnetocaloric properties [1]. This contribution will review recent DFT-based advances regarding the understanding of the interdependence between the different degrees of freedom at the first-order phase transition with a particular focus on the impact of hydrogenation on itinerant magnetism, magnetic exchange and their coupling to the vibrational properties in La-Fe-Si-based materials.<BR>[1] F. Scheibel et al., Energy Technology 6, 1397 (2018).
4:50 PM Invited
Itinerant-electron Magnetism, Spin-fluctuations, and Magnetocaloric Effect in La(Fe,Si)13-based Magnetocaloric Compounds: Asaya Fujita1; 1National Institute of Advanced Industrial Science and Technology
At a first-order phase transition point TC, equivalence of free energies in low- and high-temperature phases gives the following relation between internal energy U and entropy S ; U high – U low = TC ( S high – S low ). Namely, latent heat is governed by the energy difference ΔU between two states. In the itinerant-electron systems, like La(Fe,Si)13 or MnFe(Si,P), ΔU is enhanced by electron-correlations, while characteristic spin-fluctuations bring down TC around room temperature, resulting in high potential for magnetocaloic effect. In addition, when an energy barrier of the transition is attributed to electronic structures, its height is lower than that formed by atomic origin like a lattice deformation, resulting in smaller hysteresis. In the magnetics history, the magnetocaloric application is the first demonstration which utilizes the itinerant-electron spin fluctuations. The electronic tuning based on materials science is therefore most essential strategy in application of these materials.