Abstract
Magnetic exchange interactions in pure and vanadium (V)-doped Fe16N2 are studied within the framework of density functional theory (DFT). The Curie temperatures were obtained via both mean field approximation (MFA) and Monte Carlo (MC) calculations based on interactions that were obtained through DFT. The Curie temperature (TC) for pure Fe16N2 that was obtained under MFA is substantially larger than the experimental value, suggesting the importance of thermal fluctuations. At zero field, the calculated magnetic susceptibility shows a sharp peak at T = TC that corresponds to the presence of localized d-states. From the nature of the exchange interactions, we have determined the reason for the occurrence of the giant magnetic moment in this material, which remained a mystery for decades. Finally, we posit that Fe16N2 can also act as a satisfactory spin injector for III–V semiconductors, in addition to its application as a permanent magnet, since it has very high spin polarization (compared to elemental ferromagnets) and smaller lattice mismatch (compared to half-metallic Heusler alloys) with conventional III–V semiconductors such as GaAs and InGaAs. We demonstrate this application in the case of Fe16N2(001)/InGaAs(001) hetero-structures, which exhibit substantial spin polarization in the semiconductor (InGaAs) region. PACS number: 82.65.My, 82.20.Pm, 82.30.Lp, 82.65.Jv.
Highlights
Magnetic exchange interactions in pure and vanadium (V)-doped Fe16N2 are studied within the framework of density functional theory (DFT)
Due to their importance in the field of energy-saving technologies for the generation of electrical devices, permanent magnets that do not contain rare-earths or platinum are a current focus of research1. α′′-Fe16N2, which is a martensite, has been studied over many years, and several groups have claimed to observe giant magnetic saturation moments in it[2,3,4]
The magnetic exchange constants were obtained via a first-principles-based method and the Curie temperatures were calculated via both mean field approximation (MFA) and Monte Carlo (MC) simulation
Summary
Magnetic exchange interactions in pure and vanadium (V)-doped Fe16N2 are studied within the framework of density functional theory (DFT). Α′′-Fe16N2, which is a martensite, has been studied over many years, and several groups have claimed to observe giant magnetic saturation moments in it[2,3,4] It was first experimentally prepared by K. Ke et al.[11] studied the exchange interaction and ferromagnetic transition temperature for Fe16N2 and Co- and Ti-doped Fe16N2 using a first-principles-based method. They obtained the Curie temperature (TC) via both mean field approximation (MFA) and random phase approximation (RPA). We have studied the magnetic exchange interactions and the Curie temperatures in Fe16N2 and V-doped Fe16N2.
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