scholarly journals The Forced Magnetostrictions and Magnetic Properties of Ni2MnX (X = In, Sn) Ferromagnetic Heusler Alloys

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2017
Author(s):  
Takuo Sakon ◽  
Junya Yamazaki ◽  
Takumi Komori ◽  
Takeshi Kanomata ◽  
Yasuo Narumi ◽  
...  
Keyword(s):  
Spin Fluctuation ◽  
Heusler Alloys ◽  
Experimental Studies ◽  
Ferromagnetic State ◽  
Itinerant Ferromagnetism ◽  
Half Metallic ◽  
Frequency Space ◽  
Volume Magnetostriction ◽  
Space Frequency ◽  
The Magnetic Field

Experimental studies into the forced magnetostriction, magnetization, and temperature dependence of permeability in Ni2MnIn and Ni2MnSn ferromagnetic Heusler alloys were performed according to the spin fluctuation theory of itinerant ferromagnetism proposed by Takahashi. We investigated the magnetic field (H) dependence of magnetization (M) at the Curie temperature TC, and at T = 4.2 K, which concerns the ground state of the ferromagnetic state. The M-H result at TC was analyzed by means of the H versus M5 dependence. At 4.2 K, it was investigated by means of an Arrott plot (H/M vs. M2) according to Takahashi’s theory. As for Ni2MnIn and Ni2MnSn, the spin fluctuation parameters in k-space (momentum space, TA) and that in energy space (frequency space, T0) obtained at TC and 4.2 K were almost the same. The average values obtained at TC and 4.2 K were TA = 342 K, T0 = 276 K for Ni2MnIn and TA = 447 K, T0 = 279 K for Ni2MnSn, respectively. The forced magnetostriction at TC was also investigated. The forced linear magnetostriction (ΔL/L) and the forced volume magnetostriction (ΔV/V) were proportional to M4, which followed Takahashi’s theory. We compared the forced volume magnetostriction ΔV/V and mechanical parameter, bulk modulus K. ΔV/V is inversely proportional to K. We also discuss the spin polarization of Ni2MnIn and other magnetic Heusler alloys. The pC/pS of Ni2MnIn was 0.860. This is comparable with that of Co2MnGa, which is a famous half-metallic alloy.

scholarly journals The Characteristic Properties of Magnetostriction and Magneto-Volume Effects of Ni2MnGa-Type Ferromagnetic Heusler Alloys

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3655 ◽  
Author(s):  
Sakon ◽  
Yamasaki ◽  
Kodama ◽  
Kanomata ◽  
Nojiri ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spin Fluctuation ◽  
Heusler Alloys ◽  
Spin Fluctuations ◽  
Fluctuation Theory ◽  
Itinerant Electron ◽  
Valence Electron Concentration ◽  
Lattice Softening ◽  
The Magnetic Field ◽  
Volume Effects

In this article, we review the magnetostriction and magneto-volume effects of Ni2MnGa-type ferromagnetic Heusler alloys at the martensitic, premartensitic, and austenitic phases. The correlations of forced magnetostriction (ΔV/V) and magnetization (M), using the self-consistent renormalization (SCR) spin fluctuation theory of an itinerant electron ferromagnet proposed by Takahashi, are evaluated for the ferromagnetic Heusler alloys. The magneto-volume effect occurs due to the interaction between the magnetism and volume change of the magnetic crystals. The magnetic field-induced strain (referred to as forced magnetostriction) and the magnetization are measured, and the correlation of magnetostriction and magnetization is evaluated. The forced volume magnetostriction ΔV/V at the Curie temperature, TC is proportional to M4, and the plots cross the origin point; that is, (M4, ΔV/V) = (0, 0). This consequence is in good agreement with the spin fluctuation theory of Takahashi. An experimental study is carried out and the results of the measurement agree with the theory. The value of forced magnetostriction is proportional to the valence electron concentration per atom (e/a). Therefore, the forced magnetostriction reflects the electronic states of the ferromagnetic alloys. The magnetostriction near the premartensitic transition temperature (TP) induces lattice softening; however, lattice softening is negligible at TC. The forced magnetostriction at TC occurs due to spin fluctuations of the itinerant electrons. In the martensitic and premartensitic phases, softening of the lattice occurs due to the shallow hollow (potential barrier) of the total energy difference between the L21 cubic and modulated 10M or 14M structures. As a result, magnetostriction is increased by the magnetic field.

Electronic structure, Mechanical and Thermodynamic properties of CoYSb (Y= Cr, Mo, W) half-Heusler compounds as potential spintronic materials

2021 ◽  
Author(s):  
O. T. Uto ◽  
J. O. Akinlami ◽  
S. Kenmoe ◽  
G. A. Adebayo
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Heusler Alloys ◽  
Ferromagnetic State ◽  
Stable Phase ◽  
Type I ◽  
Electronic Density ◽  
Electronic Band ◽  
Half Metallic

Abstract We used Density Functional Theory (DFT) calculations to investigate the structural, electronic, magnetic, mechanical and thermodynamic properties of CoYSb (Y = Cr, Mo and W) compounds. These are XYZ type half-Heusler alloys, which also exist in the face centred cubic MgAgAs-type structure and conform to F¯43m space group. We computed these properties in three different atomic arrangements known as Type-I, Type-II and Type-III phases. In all these phases, the alloys were found to be in the ferromagnetic state. Furthermore, the calculated electronic band structure and the total electronic density of states indicated a metallic behaviour in CoWSb, nearly half-metallic in CoMoSb and half-metallic in CoCrSb, with a minority-spin band gap of 0.81 eV. Furthermore, the calculated mechanical properties predicted an anisotropic behaviour of these alloys in their stable phase. Finally, due to its high Debye temperature value, CoCrSb shows stronger covalent bonding than CoMoSb and CoWSb, respectively.

scholarly journals Investigation of the Itinerant Electron Ferromagnetism of Ni2+xMnGa1−x and Co2VGa Heusler Alloys

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 575 ◽  
Author(s):  
Takuo Sakon ◽  
Yuhi Hayashi ◽  
Akihito Fukuya ◽  
Dexin Li ◽  
Fuminori Honda ◽  
...  
Keyword(s):  
Field Dependence ◽  
Magnetic Moment ◽  
Ground State ◽  
Spin Fluctuation ◽  
Heusler Alloys ◽  
Ferromagnetic State ◽  
Experimental Investigations ◽  
Itinerant Electron ◽  
Arrott Plot ◽  
Temperature Dependences

Experimental investigations into the field dependence of magnetization and temperature dependences of magnetic susceptibility in Ni2+xMnGa1−x (x = 0.00, 0.02, 0.04) and Co2VGa Heusler alloy ferromagnets were performed following the spin fluctuation theory of itinerant ferromagnetism, called as “Takahashi theory”. We investigated the magnetic field dependence of magnetization at the Curie temperature TC, which is the critical temperature of the ferromagnetic–paramagnetic transition, and also at T = 5 K, which concerns the ground state of the ferromagnetic state. The field dependence of the magnetization was analyzed by means of the H vs. M5 dependence, and the field dependence of the ground state at 5 K was investigated by means of an Arrott plot (H/M vs. M2) according to the Takahashi theory. As for Ni2+xMnGa1−x, the spin fluctuation parameter in k-space (momentum space, TA) and that in energy space (T0) obtained at TC and 5 K were almost the same. On the contrary, as for Co2VGa, the H vs. M5 dependence was not shown at TC. We obtained TA and T0 by means of an Arrott plot at 5 K. We created a generalized Rhodes–Wohlfarth plot of peff/pS versus TC/T0 for the other ferromagnets. The plot indicated that the relationship between peff/pS and T0/TC followed Takahashi’s theory. We also discussed the spontaneous magnetic moment at the ground state, pS, which was obtained by an Arrott plot at 5 K and the high temperature magnetic moment, pC, at the paramagnetic phase. As for the localized ferromagnet, the pC/pS was 1. As for weak ferromagnets, the pC/pS was larger than 1. In contrast, the pC/pS was smaller than 1 by many Heusler alloys. This is a unique property of Heusler ferromagnets. Half-metallic ferromagnets of Co2VGa and Co2MnGa were in accordance with the generalized Rhodes–Wohlfarth plot with a km around 1.4. The magnetic properties of the itinerant electron of these two alloys appeared in the majority bands and was confirmed by Takahashi’s theory.

Possible half-metallic behavior of Co2−xCrxFeGe Heusler alloys: Theory and experiment

2021 ◽  
Vol 104 (1) ◽  
Author(s):  
R. Mahat ◽  
S. KC ◽  
U. Karki ◽  
J. Y. Law ◽  
V. Franco ◽  
...  
Keyword(s):  
Heusler Alloys ◽  
Metallic Behavior ◽  
Half Metallic ◽  
Theory And Experiment

scholarly journals The effect of pressure and alloying on half-metallicity of quaternary Heusler compounds CoMnYZ (Z = Al, Ga, and In)

2016 ◽  
Vol 34 (4) ◽  
pp. 905-915 ◽  
Author(s):  
M. Rahmoune ◽  
A. Chahed ◽  
A. Amar ◽  
H. Rozale ◽  
A. Lakdja ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Density Functional ◽  
Heusler Alloys ◽  
Band Gaps ◽  
Ferromagnetic Behavior ◽  
Full Potential ◽  
Energy Bands ◽  
Half Metallicity ◽  
Half Metallic ◽  
Electronic And Magnetic Properties

AbstractIn this work, first-principles calculations of the structural, electronic and magnetic properties of Heusler alloys CoMnYAl, CoMnYGa and CoMnYIn are presented. The full potential linearized augmented plane waves (FP-LAPW) method based on the density functional theory (DFT) has been applied. The structural results showed that CoMnYZ (Z = Al, Ga, In) compounds in the stable structure of type 1+FM were true half-metallic (HM) ferromagnets. The minority (half-metallic) band gaps were found to be 0.51 (0.158), 0.59 (0.294), and 0.54 (0.195) eV for Z = Al, Ga, and In, respectively. The characteristics of energy bands and origin of minority band gaps were also studied. In addition, the effect of volumetric and tetragonal strain on HM character was studied. We also investigated the structural, electronic and magnetic properties of the doped Heusler alloys CoMnYGa1−xAlx, CoMnYAl1−xInx and CoMnYGa1−xInx (x = 0, 0.25, 0.5, 0.75, 1). The composition dependence of the lattice parameters obeys Vegard’s law. All alloy compositions exhibit HM ferromagnetic behavior with a high Curie temperature (TC).

Vacancy-induced minority-spin states in half-metallic Heusler alloys

2007 ◽  
Vol 1 (5) ◽  
pp. 184-186 ◽  
Author(s):  
Kemal Özdoğan ◽  
Ersoy Şaşıoğlu ◽  
Iosif Galanakis
Keyword(s):  
Heusler Alloys ◽  
Spin States ◽  
Half Metallic ◽  
Minority Spin
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