Interdependence of Magnetic and Chemical Short-Range Order in the CrCoNi Multi-Principal Element Alloy (original) (raw)

Magnetically driven short-range order can explain anomalous measurements in CrCoNi

Proceedings of the National Academy of Sciences

The presence, nature, and impact of chemical short-range order in the multi-principal element alloy CrCoNi are all topics of current interest and debate. First-principles calculations reveal that its origins are fundamentally magnetic, involving repulsion between like-spin Co–Cr and Cr–Cr pairs that is complemented by the formation of a magnetically aligned sublattice of second-nearest-neighbor Cr atoms. Ordering models following these principles are found to predict otherwise anomalous experimental measurements concerning both magnetization and atomic volumes across a range of compositions. In addition to demonstrating the impact of magnetic interactions and resulting chemical rearrangement, the possible explanation of experiments would imply that short-range order of this type is far more prevalent than previously realized.

Magnetically driven short-range order as an explanation for anomalous measurements in CrCoNi

arXiv: Materials Science, 2020

The presence, nature, and impact of chemical short-range order in the multi-principal element alloy CrCoNi are all topics of current interest and debate. First-principles calculations reveal that its origins are fundamentally magnetic, involving repulsion between like-spin Co-Cr and Cr-Cr pairs that is complemented by the formation of a magnetically aligned sublattice of second-nearest neighbor Cr atoms. Ordering models following these principles are found to predict otherwise anomalous experimental measurements concerning both net magnetization and atomic volumes across a range of compositions. In addition to demonstrating the impact of magnetic interactions and resulting chemical rearrangement, the possible explanation of experiments would imply that short-range order of this type is far more prevalent than previously realized.

Theoretical antiferromagnetism of ordered face-centered cubic Cr-Ni alloys

Physical Review Materials, 2022

Contrary to prior calculations, the Ni-rich ordered structures of the Cr-Ni alloy system are found to be antiferromagnetic under semilocal density-functional theory. The optimization of local magnetic moments significantly increases the driving force for the formation of CrNi 2 , the only experimentally observed intermetallic phase. This structure's ab initio magnetism appears well described by a Heisenberg Hamiltonian with longitudinal spin fluctuations; itinerant Cr moments are induced only by the strength of exchange interactions. The role of magnetism at temperature is less clear and several scenarios are considered based on a review of experimental literature, specifically a failure of the theory, the existence of an overlooked magnetic phase transition, and the coupling of antiferromagnetism to chemical ordering. Implications for related commercial and high-entropy alloys are discussed for each case.

On the Nature of Anomalous Electronic and Lattice Properties of Dilute CR-Based Alloys

Journal De Physique, 1988

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Studies of the magnetic ordering in Cr+15at% Ru

Physica B: Condensed Matter, 2006

This study provides additional information to complement the magnetic phase diagram of the Cr 1Àx Ru x alloy system in the higher Ru content region where the spin-density-wave (SDW) magnetism becomes suppressed. Results from the neutron diffraction investigation on a Cr+15 at% Ru polycrystalline sample reveal that the SDW ordering is commensurate to the underlying crystallographic structure for all temperatures below the Ne´el temperature (T N ). The Ne´el temperature determined from the temperature dependences of the (1 0 0) magnetic peak intensity and the longitudinal wave velocity give T N ¼ 228 K. This temperature is significantly lower than was concluded from magnetic susceptibility and electrical resistivity studies that gave T N ¼ 270 K. r

Phase-decomposition-related short-range ordering in an Fe–Cr alloy

A redistribution of Cr atoms related to a phase decomposition (PD) caused by an isothermal annealing at 415 C in a 15.15 at.% Cr Fe–Cr alloy was studied in an ex situ way by the conversion electrons Mossbauer spectroscopy. Analysis of the spectra in terms of a twoshell model enabled the determination of probabilities of 17 different atomic configurations and average numbers of Cr atoms within the first (1NN) and the second (2NN) neighbor shells vs. annealing time, separately. The annealing-time evolution of these numbers, expressed in terms of the Cowley–Warren short-range order (SRO) parameters, was shown to follow the Johnson–Mehl–Avrami–Kolgomorov equation. The SRO parameter averaged over the 1NN–2NN shells was revealed to be linearly correlated with the average hyperfine field. Signatures in favor of the nucleation and growth mechanisms responsible for PD are also discussed.

Ferromagnetism of Cr/Mn systems

Physica B: Condensed Matter, 2002

We have investigated the magnetic ordering of Cr/Mn systems at T ¼ 0 K using real-space tight-binding approach. The magnetic moments of Cr n /Mn interfaces are calculated for n ¼ 123 overlayers in the crystallographic orientations (0 0 1), (1 1 1), and (0 1 1). The onset of magnetism depends on the faces considered. The magnetism is most favored in the (1 1 1) orientation, whereas it has the least value in (0 1 1) orientation in all systems due to the coordination. r (J.M. Khalifeh). 0921-4526/02/$ -see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 -4 5 2 6 ( 0 2 ) 0 0 8 5 2 -9

Magnetic properties of the CrMnFeCoNi high-entropy alloy

Physical Review B

We present experimental data showing that the equiatomic CrMnFeCoNi high-entropy alloy undergoes two magnetic transformations at temperatures below 100 K while maintaining its FCC structure down to 3 K. The first transition, paramagnetic to spin glass, was detected at 93 K and the second transition of the ferromagnetic type occurred at 38 K. Field-assisted cooling below 38 K resulted in a systematic vertical shift of the hysteresis curves. Strength and direction of the associated magnetization bias was proportional to the strength and direction of the cooling field and shows a linear dependence with a slope of 0.006 ± 0.001 emu/T. The local magnetic moments of individual atoms in the CrMnFeCoNi quinary FCC random solid solution were investigated by ab initio (electronic density functional theory) calculations. Results of the numerical analysis suggest that, irrespective of the initial configuration of local magnetic moments, the magnetic moments associated with Cr atoms align anti-ferromagnetically with respect to a cumulative magnetic moment of their first coordination shell. The ab initio calculations further showed that the magnetic moments of Fe and Mn atoms remain strong (between 1.5 and 2 µB) while the local moments of Ni atoms effectively vanish. These results indicate that interactions of Mn-and/or Fe-located moments with the surrounding magnetic structure account for the observed macroscopic magnetization bias.

Magnetic anisotropy as an evidence of local magnetic moments in paramagnetic phase of Cr-V alloys

AIP Advances

Chromium-rich Cr-V alloys exhibit three phases. The paramagnetic phase (P) above Néel temperature (TN), a transverse polarization spin-density-wave (SDW) phase (AF1) below TN and above the spin–flip temperature (TSF), when the longitudinal polarization SDW phase (AF2) is formed. In the paramagnetic phase, Cr exhibit a Pauli susceptibility with weak temperature dependence. Otherwise, the introduction of small amounts of V in Cr not only decreases TN continuously, but also induces a Curie-Weiss behavior (CW) that we associate with local magnetic moments. This behavior is limited up to 0.67%V and magnetic fields of 15 kOe and was also observed for different Cr alloys. The origin of local magnetic moments has been associated with the establishment of local spin-density waves (LSDW) around V impurities. In this work, we presented an investigation of the effects of local magnetic moments in antiferromagnetic phases in Cr-V alloys. The magnetic susceptibility measurements around the spin–f...