Bulk and element-specific magnetism of medium-entropy and high-entropy Cantor-Wu alloys

Abstract

Magnetic Compton scattering, x-ray magnetic circular dichroism spectroscopy, and bulk magnetometry measurements are performed on a set of medium-(NiFeCo and NiFeCoCr) and high-entropy (NiFeCoCrPd and NiFeCoCrMn) Cantor-Wu alloys. The bulk spin momentum densities determined by magnetic Compton scattering are remarkably isotropic, and this is a consequence of the smearing of the electronic structure by disorder scattering of the electron quasiparticles. Nonzero x-ray magnetic circular dichroism signals are observed for every element in every alloy indicating differences in the populations of the majority and minority spin states implying finite magnetic moments. When Cr is included in the solid solution, the Cr spin moment is unambiguously antiparallel to the total magnetic moment, while a vanishingly small magnetic moment is observed for Mn, despite calculations indicating a large moment. Some significant discrepancies are observed between the experimental bulk and surface magnetic moments. Despite the lack of quantitative agreement, the element-specific surface magnetic moments seem to be qualitatively reasonable.

Magnetic, electrical and mechanical properties of Fe40Mn40Co10Cr10 high entropy alloy

“…A strong magnetic frustration due to the fluctuations of Mn and Cr magnetic moments and their antiferromagnetic coupling to Fe and Co is expected to significantly reduce the overall magnetic moment of the system since these atoms correspond to 50% of the structure. Recent X-ray magnetic circular dichroism (XMCD) studies on high entropy alloys showed that that the bulk magnetic moments can be strongly suppressed with increasing concentration of antiferromagnetically coupled elements in the solid solution 33 .…”

“…(3) Field dependence of the magnetization indicated that the material acts differently than magnetically homogeneous ferromagnetic material where the magnetic moment is expected to saturate with an increasing magnetic field. In general, many magnetic states such as ferromagnetism 3 , 20 , 46 , ferrimagnetism 14 , 33 , antiferromagnetism 12 , and paramagnetism 47 are present in high entropy alloys materials due to complex magnetic couplings of constituent 3d elements. Often subtle compositional changes in 4 and 5 element systems stabilize one magnetic phase over the other.…”

Tuning the Magnetic Properties of the CrMnFeCoNi Cantor Alloy

“…Billington et al [48] carried out a detailed study of the element specific magnetic properties of the Cantor alloy and certain Cantor alloy variants using a combination of magnetic Compton scattering, x-ray magnetic circular dichroism spectroscopy, and bulk magnetization measurements, noting significant discrepancies between computational and experimental results when examining magnetic moments. However, in compounds where computation and experiment disagreed, computational moments were much larger than experimental ones.…”

Magnetic properties of equiatomic CrMnFeCoNi

“…Much work has been done regarding the mechanical properties of Cantor alloys [8][9][10][11][12][13] , as well as the magnetic properties of similar compounds 6,7,[14][15][16][17][18][19][20][21][22][23] , but fewer studies have examined the magnetic properties of the original CrMnFeCoNi alloy [24][25][26][27][28] . Of its component elements, Cr and Mn are antiferromagnetic with T N = 311 K 29 and T N = 100 K 30 respectively, while Fe, Co, and Ni are ferromagnetic with T C = 1043 K, T C = 1394 K, and T C = 631 K, respectively 31 .…”