TY - JOUR AU - Huang, Shuo AU - Dastanpour, Esmat AU - Strom, Valter AU - Varga, Lajos Károly AU - Eriksson, Olle AU - Jin, Hongyun AU - Vitos, Levente TI - Lattice and spin entropy changes in B2-type magnetocaloric Al-Mn-Ni alloy JF - JOURNAL OF PHYSICS D-APPLIED PHYSICS J2 - J PHYS D APPL PHYS VL - 58 PY - 2025 IS - 7 PG - 7 SN - 0022-3727 DO - 10.1088/1361-6463/ad9591 UR - https://m2.mtmt.hu/api/publication/35668057 ID - 35668057 N1 - Funding Agency and Grant Number: Swedish Foundation for Strategic Research, Swedish Research Council [2017-06474, 2019-04971, 2022-04758]; Sweden's Innovation Agency (VINNOVA) [2019-05111]; Swedish Energy Agency; STandUPP; WISE; Wallenberg Foundation Materials Science (OTKA ) [128229]; ESSANCE; Carl Tryggers Foundation [19:325, 20:474]; Hungarian Scientific Research Fund; Swedish Research Council [2018-05973]; Swedish Research Council [2022-04758] Funding Source: Swedish Research Council; Vinnova [2019-05111] Funding Source: Vinnova Funding text: This research was supported by Swedish Foundation for Strategic Research, Swedish Research Council (Grant Nos. 2017-06474, 2019-04971, and 2022-04758), Sweden's Innovation Agency (VINNOVA Grant No. 2019-05111), Swedish Energy Agency, STandUPP, WISE, Wallenberg Foundation Materials Science, eSSANCE, Carl Tryggers Foundation (Grant Nos. 19:325, 20:474) and Hungarian Scientific Research Fund (OTKA Grant No. 128229). The computations were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC) at Linkoeping and Stockholm partially funded by the Swedish Research Council through Grant Agreement No. 2018-05973. AB - Understanding the electronic, lattice, and magnetic contributions to the magnetocaloric effect in magnetic materials can help to elucidate and optimize their performance. In this work, the structural and magnetocaloric properties of Al-Mn-Ni alloy are experimentally determined and theoretically analyzed based on ab initio calculations. The dominating B2 phase associated with the Mn-rich sublattice is found to be responsible for the observed magnetocaloric properties. The magnetic entropy change, refrigerant capacity, and adiabatic temperature change are evaluated. Through the analysis of the data, we find that for the B2 phase, changing from ferromagnetic to paramagnetic configurations results in a pronounced elastic hardening despite the volume expansion. The decrease in lattice entropy is significant and contributes negatively to the magnetic and electronic entropy changes. Our work emphasizes the critical role of the lattice sector in the magnetocaloric effect, and provides an in-depth understanding of the individual entropy terms in magnetic solid solutions. LA - English DB - MTMT ER - TY - JOUR AU - Temesi, Otto K. AU - Chinh, Nguyen Q. AU - Vitos, Levente AU - Varga, Lajos Károly TI - Estimation of Hardness of Single-Phase Metallic Alloys JF - CRYSTALS J2 - CRYSTALS VL - 15 PY - 2025 IS - 2 PG - 15 SN - 2073-4352 DO - 10.3390/cryst15020156 UR - https://m2.mtmt.hu/api/publication/35809100 ID - 35809100 N1 - Funding Agency and Grant Number: Government of Hungary for support from the Market-driven R&D and Innovation [2020-1.1.2-PIACI-KFI-2020-00025]; Government of Hungary Funding text: This research was supported by the Government of Hungary for support from the Market-driven R&D and Innovation grant (2020-1.1.2-PIACI-KFI-2020-00025). AB - First, we discuss a common feature of single-phase pure metals and amorphous and high-entropy alloys: the maximum value of hardness corresponding to a valence electron count (VEC) value of around 6.5-7. This correlation is explained by the coincidence that by subtracting the number of sp valence electrons (Nsp = 2) from the VEC we obtain the maximal number of unpaired d electrons, Nd = 4.5-5 in the 3d, 4d, and 5d rows of transition elements. These unpaired d electrons form orbital overlap bonding, which is stronger than the isotropic metallic bonds of a delocalized electron cloud. The more unpaired d electrons there are, the higher the bonding strength. Second, we will discuss the hardness formulas derived from cohesion energy and shear modulus. We will demonstrate that both types of formulas originate in the electrostatic energy density of metallic bonds, expressing a 1/R4 dependence. Finally, we show that only two parameters are sufficient to estimate hardness: the atomic radius and the cohesion-based valence. In the case of alloys, our formula gives a lower bound on the hardness only. It is not suitable for calculation of the hardness increase caused by solid solution, grain size, precipitation, and phase mixture. LA - English DB - MTMT ER - TY - JOUR AU - Temesi, O.K. AU - Karacs, A. AU - Nguyen Quang, Chinh AU - Varga, Lajos Károly TI - Temperature Dependence of Hardness of High Entropy Alloys JF - METALS J2 - METALS-BASEL VL - 15 PY - 2025 IS - 6 PG - 24 SN - 2075-4701 DO - 10.3390/met15060623 UR - https://m2.mtmt.hu/api/publication/36221819 ID - 36221819 N1 - Funding Agency and Grant Number: Government of Hungary; [2020-1.1.2-PIACI-KFI-2020-00025] Funding text: This research was funded by the Government of Hungary with support from the Market-driven R&D and Innovation grant (2020-1.1.2-PIACI-KFI-2020-00025). LA - English DB - MTMT ER - TY - JOUR AU - Dastanpour, E. AU - Huang, S. AU - Schönecker, S. AU - Ström, V. AU - Varga, Lajos Károly AU - Eriksson, O. AU - Vitos, Levente TI - Magnetocaloric properties of ternary Al-Mn-Co alloys JF - JOURNAL OF ALLOYS AND COMPOUNDS J2 - J ALLOY COMPD VL - 1036 PY - 2025 PG - 9 SN - 0925-8388 DO - 10.1016/j.jallcom.2025.182006 UR - https://m2.mtmt.hu/api/publication/36239465 ID - 36239465 N1 - Funding Agency and Grant Number: Swedish Foundation for Strategic Research; Swedish Research Council [2022-06725, 2019-04971, 2022-04758]; Sweden's Innovation Agency (VINNOVA) [2019-5111]; Carl Tryggers Foundation [19:325, 20:474]; STandUP and eSSENCE as well as the Swedish Research Council; European Research Council (ERC); Wallenberg Initiative Materials Science for Sustainability (WISE) - Knut and Alice Wallenberg Foundation (KAW); Swedish Research Council [2022-04758, 2019-04971] Funding Source: Swedish Research Council Funding text: This work was supported by the Swedish Foundation for Strategic Research, the Swedish Research Council (Grant Agreement No. 2019-04971 and 2022-04758) , the Sweden's Innovation Agency (VINNOVA Grant No. 2019-5111) , the Carl Tryggers Foundation (Grant Agreement No. 19:325 and 20:474) . O.E. acknowledges support from STandUP and eSSENCE as well as the Swedish Research Council, the European Research Council (ERC) and the Wallenberg Initiative Materials Science for Sustainability (WISE) funded by the Knut and Alice Wallenberg Foundation (KAW) . The computations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) at Linkoping partially funded by the Swedish Research Council through grant agreement no. 2022-06725. The authors would like to acknowledge Haireguli Aihemaiti in KTH Stockholm who assisted in ab initio calculations. LA - English DB - MTMT ER - TY - JOUR AU - Dastanpour, Esmat AU - Aihemaiti, Haireguli AU - Huang, Shuo AU - Strom, Valter AU - Varga, Lajos Károly AU - Vitos, Levente TI - Structural and Ferromagnetic Response of B2-Type Al45Mn41.8X13.2 (X = Fe, Co, Ni) Alloys JF - MAGNETOCHEMISTRY J2 - MAGNETOCHEMISTRY VL - 11 PY - 2025 IS - 8 PG - 10 SN - 2312-7481 DO - 10.3390/magnetochemistry11080067 UR - https://m2.mtmt.hu/api/publication/36331298 ID - 36331298 N1 - Funding Agency and Grant Number: Swedish Foundation for Strategic Research; Wallenberg Initiative Materials Science for Sustainability (WISE) - Knut and Alice Wallenberg Foundation (KAW); Formas-a Swedish Research Council for Sustainable Development [2023-00543]; Carl Tryggers Foundation [CTS 22:1970]; Swedish Research Council [2022-06725]; [SM23-0041]; Formas [2023-00543] Funding Source: Formas; Vinnova [2023-00543] Funding Source: Vinnova Funding text: This work was supported by the Swedish Foundation for Strategic Research (SM23-0041), the Wallenberg Initiative Materials Science for Sustainability (WISE) funded by the Knut and Alice Wallenberg Foundation (KAW), the Formas-a Swedish Research Council for Sustainable Development (2023-00543), and the Carl Tryggers Foundation (CTS 22:1970). The computations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) at the National Supercomputing Centre (NSC, Tetralith cluster), partially funded by the Swedish Research Council through Grant Agreement No. 2022-06725. AB - To our knowledge, no magnetic B2 phase in the Al-Mn system of near-equiatomic compositions has been reported so far. Here, we investigate the structural and magnetic characteristics of Al45Mn41.8X13.2 (X = Fe, Co or Ni) alloys. We demonstrate that adding 13.2 atomic percent magnetic 3d metal to AlMn stabilizes a ferromagnetic B2 structure, where Al and X occupy different sublattices. We employ density functional theory calculations and experimental characterizations to underscore the role of the late 3d metals for the phase stability of the quasi-ordered ternary systems. We show that these alloys possess large local magnetic moments primarily due to Mn atoms partitioned to the Al-free sublattice. The revealed magneto-chemical effect opens alternative routes for tailoring the magnetic properties of B2 intermetallic compounds for various magnetic applications. LA - English DB - MTMT ER - TY - JOUR AU - Bakonyi, Imre AU - Czeschka, F.D. AU - Isnaini, Vandri Ahmad AU - Krupp, A.T. AU - Gubicza, Jenő AU - Varga, Lajos Károly AU - Péter, László TI - High-field magnetoresistance measurements on Ni75Co25 and Ni40Co60 alloys at 3 K and 300 K JF - JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS J2 - J MAGN MAGN MATER VL - 591 PY - 2024 PG - 9 SN - 0304-8853 DO - 10.1016/j.jmmm.2023.171683 UR - https://m2.mtmt.hu/api/publication/34453578 ID - 34453578 AB - In the present work, a detailed field dependence of the resistivity of Ni75Co25 and Ni40Co60 bulk alloys was measured at T = 3 K and 300 K up to high magnetic fields. The focus of the study was to determine the anisotropic magnetoresistance (AMR) and to get a quantitative description of the field-induced resistivity change, the latter not yet being available for Ni-Co alloys. The AMR parameters were derived from the resistivity data in the magnetically saturated (monodomain) state by using the Kohler analysis. The values of the AMR ratio were found to be close to the relevant previous data both at low and high temperatures. Due to the measurement precision and careful data evaluation, our AMR data obtained on well-characterized samples can be considered as reference values for the bulk state of the investigated compositions. In addition, also the resistivity anisotropy splitting was determined. The experimentally found field dependence of the resistivity at both T = 3 K and 300 K was found to be at variance with the current theoretical descriptions both for the resistivity increase due to the ordinary magnetoresistance effect being significant at T = 3 K and for the resistivity decrease due to the magnon suppression process at T = 300 K, invoking for a refinement of theory in both cases. LA - English DB - MTMT ER - TY - JOUR AU - Kocsis, Bence AU - Windisch, Márk AU - Mészáros, István AU - Varga, Lajos Károly TI - 3D printing parameters optimization for Fe-6.5 wt%Si JF - JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS J2 - J MAGN MAGN MATER VL - 592 PY - 2024 PG - 5 SN - 0304-8853 DO - 10.1016/j.jmmm.2024.171829 UR - https://m2.mtmt.hu/api/publication/34562195 ID - 34562195 LA - English DB - MTMT ER - TY - JOUR AU - Dastanpour, E. AU - Huang, S. AU - Ström, V. AU - Varga, Lajos Károly AU - Vitos, L. AU - Schönecker, S. TI - An assessment of the Al50Cr21-xMn17+xCo12 (x=0, 4, 8) high-entropy alloys for magnetocaloric refrigeration application JF - JOURNAL OF ALLOYS AND COMPOUNDS J2 - J ALLOY COMPD VL - 984 PY - 2024 PG - 10 SN - 0925-8388 DO - 10.1016/j.jallcom.2024.173977 UR - https://m2.mtmt.hu/api/publication/35020571 ID - 35020571 LA - English DB - MTMT ER - TY - JOUR AU - Temesi, O.K. AU - Varga, Lajos Károly AU - Nguyen Quang, Chinh AU - Vitos, Levente TI - Prediction of the Cohesion Energy, Shear Modulus and Hardness of Single-Phase Metals and High-Entropy Alloys JF - MATERIALS J2 - MATERIALS VL - 17 PY - 2024 IS - 11 PG - 19 SN - 1996-1944 DO - 10.3390/ma17112728 UR - https://m2.mtmt.hu/api/publication/35059084 ID - 35059084 LA - English DB - MTMT ER - TY - JOUR AU - Kiss, László Ferenc AU - Varga, Lajos Károly AU - Gubicza, Jenő AU - Péter, László AU - Bakonyi, Imre TI - Influence of demagnetizing effects on the magnetization curves of finite-size rectangular slabs JF - EUROPEAN PHYSICAL JOURNAL PLUS J2 - EUR PHYS J PLUS VL - 139 PY - 2024 IS - 9 PG - 10 SN - 2190-5444 DO - 10.1140/epjp/s13360-024-05652-8 UR - https://m2.mtmt.hu/api/publication/35394968 ID - 35394968 AB - According to some recent studies, the magnetoresistance curves of ferromagnetic strip-shaped samples can significantly differ depending on whether the in-plane external applied magnetic field H is oriented in parallel to either the long or the short edge of the strip. To address this problem, in the present work magnetization curves M ( H ) were measured for similarly shaped samples with both magnetic field orientations used in the magnetoresistance measurements. It was found that the M ( H ) curves strongly depend on the saturation magnetization and shape of the samples as well as on the magnetic field orientations. For some samples with sufficiently large saturation magnetization, the effective demagnetizing factors could be deduced from the measured M ( H ) curves. By considering the investigated samples as a ferromagnetic slab, and approximating them with a general ellipsoid, the demagnetizing factors were calculated from known formulae and compared to the experimental values. A fairly good matching was observed, although the latter data were systematically slightly larger, certainly due to the not completely homogeneous magnetization within the rectangular slab as opposed to the case of a general ellipsoid. The differences in the M ( H ) curves for the two orientations of the magnetic field could be completely attributed to demagnetizing effects. LA - English DB - MTMT ER -