Magnetic transformation of Mn from anti-ferromagnetism to ferromagnetism in FeCoNiZMnx (Z = Si, Al, Sn, Ge) high entropy alloys

• We design high entropy alloys (HEAs) with different induction elements (Si/Al/Sn). In order to keep the crystal structure invariant and to investigate how the increment in saturation magnetization (Ms) is caused only by the change of electron spin state, each set of HEAs contains a different amount of Mn. Synergistic effects among induction elements that induce the magnetic transformation of Mn from anti-ferromagnetism to ferromagnetism are found. Ms of added Mn reduces when a particular induction element (Si0.4/Al0.4/Sn0.4) exists, while a larger increment of Ms appears when two induction elements coexist, Si0.4Al0.4 (25.79 emu/g) and Sn0.4Al0.4 (15.43 emu/g). This is reflected in the microcosmic magnetic structure for the emergence of closed domains due to large demagnetization energy, which is confirmed by the Lorentz transmission electron microscope (LTEM) data. The calculated magnetic moments and the exchange integral constants from density functional theory based on the Exact Muffin-Tin Orbits formalism reveal that the magnetic state and the strength of ferromagnetic and anti-ferromagnetic coupling determine the variation of Ms in different chemical environments. The difference in energy levels of coexisting multiple induction elements also leads to a larger increment of Ms, Si0.4Al0.4Sn0.4 (29.78 emu/g), and Si0.4Al0.4Ge0.4Sn0.4 (31.00 emu/g).

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

Nyckelord

Density functional theory

Exchange integral constants

High entropy alloy

Magnetic moment

Magnetic transformation

Binary alloys

Crystal structure

Crystallography

Entropy

Ferromagnetic materials

High-entropy alloys

Magnetic moments

Magnetic structure

Manganese

Saturation magnetization

Silicon

Spin dynamics

Transmission electron microscopy

Chemical environment

Demagnetization energy

Electron spin state

Exchange integrals

Ferromagnetic and anti-ferromagnetic

Magnetic state

Magnetic transformations

Synergistic effect

Ferromagnetism

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