Using Density Functional Theory (DFT) calculations and Monte-Carlo (MC) simulations, we investigate the recently reported magnetic transition in B2 Al–Cr–Co alloys. The Cr sublattice is alloyed with different amounts of Co in the antiferromagnetic (AFM) B2 AlCr binary alloy and the resulting exchange interactions are analyzed within the Heisenberg Hamiltonian framework. DFT results reveal that at low Co concentrations the system favors the AFM order, while at high Co contents a transition to the ferromagnetic (FM) state is observed. Within the FM stability field, the Curie temperature (T_C), obtained within the mean-field approximation, is below ∼160 K and decreases with Co concentration. The calculated exchange parameters evolve systematically with Co content, and the trends are consistent with the DFT total energies. The magnetic configurations obtained from MC simulations follow the DFT results at low Cr levels but predict a spin-glass behavior for alloys containing more than 40 at. % Co on Cr sublattice. These findings provide a fundamental understanding of how the chemistry-driven changes in exchange interactions affect magnetism in the B2 Al–Cr–Co alloys.

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.

We investigate how the Al content in Alx(Mn0.76Co0.24)1-x (x = 0.45, 0.50, 0.55) alloys and the Mn/Co ratio in Al0.50MnyCo0.50-y (y = 0.36, 0.38, 0.40) alloys affect the magnetic properties. Structural and magnetic investigations by experiments, Thermo-Calc, and ab initio calculations show a dual-phase microstructure containing different fractions of a paramagnetic body-centered cubic (BCC) solid solution and a ferromagnetic B2 phase. The BCC/B2 phase fraction is sensitive to the Al content which strongly affects the saturation magnetization, magnetic transition temperature, and magnetocaloric properties. The magnetocaloric properties of the Al0.50Mn0.38Co0.12 alloy show peak values around 430 K with a magnetic entropy change of 0.71 Jkg−1K−1, an adiabatic temperature change of 0.40 K, and a refrigeration capacity of 25.56 Jkg−1 under a magnetic field of 650 kAm−1 (0.82 T). These results open new possibilities for identifying promising medium-entropy alloys for magnetocaloric applications.

Recently, we reported an antiferromagnetic ground state for equiatomic Al-Cr in the B2 structure. Here, by a joint theoretical–experimental study, we investigate the effect of Co additions to the Al-Cr alloy with the aim to synthesize a ferromagnetic B2 phase. Al50Cr38Co12 (at.%) is prepared by arc melting from high-purity raw materials and solidifies into a combination of a Co-enriched B2 phase, a Co-depleted BCC phase, and an Al8Cr5 intermetallic phase. The as-cast alloy is ferromagnetic with a Curie point of 260 K, primarily due to the presence of about 54% B2 phase. Subsequent annealing decreases the fraction of the B2 phase to 27% with depletion of Cr from 20.2 at.% to 16.1 at.%, which leads to a reduction in its ferromagnetic behavior. Calculations based on Density Functional Theory (DFT) predict a corresponding decrease in the total magnetic moment and Curie temperature of the B2 phase by annealing. The present findings highlight the roles of Cr and Co in facilitating the formation of a metastable ferromagnetic B2 phase in this alloy. 

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.

This study investigates the magnetocaloric potential of the Al50Cr21-xMn17+xCo12 (x=0, 4, 8 at%) high-entropy alloy (HEA) series using integrated experimental and theoretical approaches. Structural analysis by X-ray diffraction and scanning electron microscopy indicate a dual phase containing B2 and body-centered cubic (BCC) structures. Magnetic characterization shows an approximately linear decrease in saturation magnetization and Curie temperature with increasing Cr content. Curie temperatures calculated by Monte Carlo simulations suggest that the measured magnetic properties originate from the B2 phase rather than the BCC phase. The enhanced magnetocaloric effect with decreasing Cr content highlights the attractiveness of HEAs in magnetocaloric applications.

Multi-component alloys have received increasing interest for functional applications in recent years. Here, we explore the magnetocaloric response for Al-Cr-Mn-Co medium-entropy alloys by integrated theoretical and experimental methods. Under the guidance of thermodynamic and ab initio calculations, a dual-phase system with large magnetic moment, i.e., Al₅₀Cr₁₉Mn₁₉Co₁₂, is synthesized, and the structural and magnetocaloric properties are confirmed via characterization. The obtained results indicate that the selected alloy exhibits a co-continuous mixture of a disordered body-centered cubic and an ordered B2 phase. The ab initio and Monte Carlo calculations indicate that the presence of the ordered B2 phase is responsible for the substantial magnetocaloric effect. The magnetization measurements demonstrated that this alloy undergoes a second-order magnetic transition with the Curie temperature of ∼300 K. The magnetocaloric properties are examined using magnetic entropy change, refrigeration capacity, and adiabatic temperature change. The property-directed strategy explored here is intended to contribute to the study of potential multi-component alloys in magnetocaloric applications.

We have conducted an in-depth study of the magnetic phase due to a spinodal decomposition of the BCC phase of a CrFe-rich composition. This magnetic phase is present after casting (arc melting) or water quenching after annealing at 1250 degrees C for 24 h but is entirely absent after annealing in the interval 900-1100 degrees C for 24 h. Its formation is favored in the temperature interval ca 450-550 degrees C and loses magnetization above 640 degrees C. This ferromagnetic-paramagnetic transition is due to a structural transformation from ferromagnetic BCC into paramagnetic sigma and FCC phases. The conclusion from measurements at different heating rates is that both the transformation leading to the increase of the magnetization due to the spinodal decomposition of the parent phase and the vanishing magnetization at 640 degrees C are diffusion controlled.

The present work investigates how the vanadium (V) content in a series of Al50V (x) (Cr0.33Mn0.33Co0.33)((50-x)) (x = 12.5, 6.5, 3.5, and 0.5 at.%) high-entropy alloys affects the local magnetic moment and magnetic transition temperature as a step towards developing high-entropy functional materials for magnetic refrigeration. This has been achieved by carrying out experimental investigations on induction melted alloys and comparison to ab initio and thermodynamic calculations. Structural characterization by x-ray diffraction and scanning electron microscopy indicates a dual-phase microstructure containing a disordered body-centered cubic (BCC) phase and a B2 phase with long-range order, which significantly differ in the Co and V contents. Ab initio calculations demonstrate a weaker magnetization and lower magnetic transition temperature (T

In this research, thermal stability, corrosion performance, hardness (H), and Young modulus (E) of Ni60Nb40, Ni60Nb20Zr20, and Ni60Nb40 amorphous ribbons were evaluated during the differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests, and nanoindentation technique, respectively. Results showed that the onset crystallization temperatures (To) of Ni60Nb40, Ni60Nb20Zr20, and Ni60Nb40 amorphous ribbons were 632 °C, 593 °C and 476 °C, respectively. It is determined that the higher Nb content increases the thermal stability against crystallization. Evaluation of corrosion resistance during potentiodynamic polarization test showed the polarization resistance value of 936, 49, and 16 MΩ.cm2 for Ni60Nb40, Ni60Nb20Zr20, and Ni60Nb40 alloys, respectively. These results imply that the substitution of Zr with Nb enhances the thermal stability and corrosion resistance of Ni-Nb-Zr amorphous ribbons. Moreover, the H and E for Ni60Nb40, Ni60Nb20Zr20, and Ni60Nb40 amorphous ribbons were 171.3 and 15.01 GPa, 160.41 and 12.16 GPa, and, 188.52 and 14.13 GPa, respectively. It means complete substitution of Zr by Nb in Ni-Nb-Zr amorphous ribbons shows the highest hardness which is related to the Ni60Nb40 amorphous ribbon