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 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, O.K. AU - Karacs, A. AU - Nguyen Quang, Chinh AU - Varga, Lajos Károly TI - Thermal Softening Measurements of Refractory High-Entropy Alloys JF - MATERIALS J2 - MATERIALS VL - 17 PY - 2024 IS - 23 PG - 13 SN - 1996-1944 DO - 10.3390/ma17235718 UR - https://m2.mtmt.hu/api/publication/35645105 ID - 35645105 N1 - Export Date: 07 January 2025 LA - English DB - MTMT ER - TY - JOUR AU - Temesi, Ottó AU - Varga, Lajos Károly AU - Gulyás, Gábor TI - Az anyagtudományi kutatások ipari jövője: az innováció hétköznapi lépései a gyakorlatban a tudomány, a technológia és az ipar határán JF - FIZIKAI SZEMLE J2 - FIZIKAI SZEMLE VL - 74 PY - 2024 IS - 12 SP - 402 EP - 412 PG - 11 SN - 0015-3257 UR - https://m2.mtmt.hu/api/publication/35629928 ID - 35629928 LA - Hungarian DB - MTMT ER - TY - JOUR AU - Temesi, Ottó K. AU - Varga, Lajos Károly AU - Nguyen Quang, Chinh AU - Vitos, Levente TI - Ductility Index for Refractory High Entropy Alloys JF - CRYSTALS J2 - CRYSTALS VL - 14 PY - 2024 IS - 10 PG - 19 SN - 2073-4352 DO - 10.3390/cryst14100838 UR - https://m2.mtmt.hu/api/publication/35492351 ID - 35492351 AB - The big advantage of refractory high entropy alloys (RHEAs) is their strength at high temperatures, but their big disadvantage is their brittleness at room temperature, which prevents their machining. There is a great need to classify the alloys in terms of brittle-ductile (B-D) properties, with easily obtainable ductility indices (DIs) ready to help design these refractory alloys. Usually, the DIs are checked by representing them as a function of fraction strain, ε. The critical values of DI and ε divide the DI—ε area into four squares. In the case of a successful DI, the points representing the alloys are located in the two diagonal opposite squares, well separating the alloys with (B-D) properties. However, due to the scatter of the data, the B-D separation is not perfect, and it is difficult to establish the critical value of DI. In this paper, we solve this problem by replacing the fracture strain parameter with new DIs that scale with the old DIs. These new DIs are based on the force constant and amplitude of thermal vibration around the Debye temperature. All of them are easily available and can be calculated from tabulated data. 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 N1 - Export Date: 07 January 2025 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 - 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 - 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 N1 - Funding Agency and Grant Number: Swedish Foundation for Strategic Research; Swedish Research Council [2017-06474, 2019-04971, 2022-04758, 2022-06725]; Sweden's Innovation Agency (VINNOVA) [2019-05111]; Carl Tryggers Foundation [19:325, 20:474]; Swedish Energy Agency; Vinnova [2019-05111] Funding Source: Vinnova; Swedish Research Council [2022-04758] 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. 2017-06474, 2019-04971, 2022-04758) , the Sweden's Innovation Agency (VINNOVA Grant No. 2019-05111) , the Carl Tryggers Foundation (Grant Agreement No. 19:325 and 20:474) , and the Swedish Energy Agency. 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. 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 N1 - Export Date: 19 February 2024 CODEN: JMMMD Correspondence Address: Kocsis, B.; Széchenyi István University, 1. Egyetem Tér, Hungary; email: kocsis.bence@ga.sze.hu Funding details: Nemzeti Kutatási, Fejlesztési és Innovaciós Alap, NKFIA, TKP2021 Funding details: Széchenyi István Egyetem, SZE, TKP2021-NVA-23 Funding text 1: Supported by the ÚNKP-23-4-I- SZE -23 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund . The research presented in this paper was funded by the “Thematic Excellence Programme 2021 ( TKP2021 ) – National Defence, National Security Subprogramme – Research on military systems resilience at Széchenyi István University ( TKP2021-NVA-23 )” project. 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 N1 - Export Date: 07 January 2025; CODEN: JMMMD 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 - Huang, S. AU - Dastanpour, E. AU - Schönecker, S. AU - Ström, V. AU - Chai, G. AU - Kiss, László Ferenc AU - Varga, Lajos Károly AU - Jin, H. AU - Eriksson, O. AU - Vitos, Levente TI - Combinatorial design of partial ordered Al-Cr-Mn-Co medium-entropy alloys for room temperature magnetic refrigeration applications JF - APPLIED PHYSICS LETTERS J2 - APPL PHYS LETT VL - 123 PY - 2023 IS - 4 PG - 7 SN - 0003-6951 DO - 10.1063/5.0160477 UR - https://m2.mtmt.hu/api/publication/34090189 ID - 34090189 N1 - Export Date: 08 March 2024; CODEN: APPLA LA - English DB - MTMT ER -