METAMAGNETISM AND SPIN FLUCTUATIONS IN Co-BASED INTERMETALLIC COMPOUNDS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 788-793 ◽  
Author(s):  
TSUNEAKI GOTO ◽  
TOSHIRO SAKAKIBARA
Keyword(s):  
Ground State ◽  
High Field ◽  
Spin Fluctuation ◽  
Spin Fluctuations ◽  
Itinerant Electron ◽  
Metamagnetic Transition ◽  
Paramagnetic Region ◽  
High Field Magnetization ◽  
Transition Field ◽  
Fluctuation Model

High field magnetization and susceptibility of Co-based compounds Y(Co1−xA1x)2 are investigated in the paramagnetic region 0≤x≤0.11. In all the region, a sharp metamagnetic transition is observed, while the susceptibility shows a maximum at finite temperature Tmax. The transition field Hc exhibits a positive shift proportional to T2 with temperature. The Hc in the ground state is found to be proportional to Tmax. The experimental results are discussed with a new theory for itinerant electron metamagnetism based on the spin fluctuation model.

Ground state of Er3+ ions in ErNi5 as studied by high field magnetization

1992 ◽  
Vol 177 (1-4) ◽  
pp. 291-294 ◽  
Author(s):  
R.J. Radwański ◽  
J.J.M. Franse ◽  
D. Gignoux ◽  
F.E. Kayzel ◽  
C. Marquina ◽  
...  
Keyword(s):  
Ground State ◽  
High Field ◽  
Field Magnetization ◽  
High Field Magnetization

scholarly journals HIGH-FIELD MAGNETIZATION IN THE MOTT-HUBBARD SYSTEM (Y, Ca)VO3

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3058-3061 ◽  
Author(s):  
H. NAKOTTE ◽  
A. M. ALSMADI ◽  
H. KAWANAKA ◽  
K. KINDO ◽  
K. GOTO
Keyword(s):  
Ground State ◽  
Magnetization Curve ◽  
High Field ◽  
Inflection Point ◽  
Calcium Content ◽  
Insulator Transition ◽  
Pulsed Magnetic Fields ◽  
Magnetic Ground State ◽  
High Field Magnetization ◽  
Metal To Insulator Transition

We measured the magnetization of Y 1-x Ca x VO 3 compounds with 0 Ω × Ω, 0.6 in pulsed magnetic fields up to 56 T. YVO 3 exhibits a slightly S-shaped magnetization curve with an inflection point at B c = 42 T . the critical field B c was found to decrease with increasing calcium content, and no sign of an S-shape is seen for the compound with x = 0.6, which is at the boundary of the metal-to-insulator transition. Our data provide further evidence that the metal-to-insulator transition in this system coincides with the transition from a paramagnetic to a magnetic ground state.

High-Field Magnetization of PrCu6and PrNi5with the Singlet Ground State

1998 ◽  
Vol 67 (7) ◽  
pp. 2553-2554 ◽  
Author(s):  
Kiyohiro Sugiyama ◽  
Miho Nakashima ◽  
Atsushi Koyanagi ◽  
Shingo Araki ◽  
Koichi Kindo ◽  
...  
Keyword(s):  
Ground State ◽  
High Field ◽  
Singlet Ground State ◽  
Field Magnetization ◽  
High Field Magnetization

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.

High Field Magnetization of Singlet Ground State System Cs3Cr2X9(X=Cl, Br) up to 40 T

1989 ◽  
Vol 58 (3) ◽  
pp. 1021-1026 ◽  
Author(s):  
Yoshitami Ajiro ◽  
Hikomitsu Kikuchi ◽  
Toshiya Inami ◽  
Toshiro Sakakibara ◽  
Tsuneaki Goto
Keyword(s):  
Ground State ◽  
High Field ◽  
State System ◽  
Singlet Ground State ◽  
Field Magnetization ◽  
High Field Magnetization

ZERO—POINT SPIN FLUCTUATION EFFECTS IN ANHARMONIC WEAK ITINERANT ELECTRON MAGNETS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 585-588 ◽  
Author(s):  
ALEXANDER SOLONTSOV
Keyword(s):  
Inelastic Neutron Scattering ◽  
Spin Fluctuation ◽  
Landau Theory ◽  
Zero Point ◽  
Thermal Fluctuations ◽  
Inelastic Neutron ◽  
Spin Fluctuations ◽  
Itinerant Electron ◽  
Fluctuation Effects

The spin fluctuation theory of weak itinerant magnets is critically reviewed and is shown to be well established in the weak spin anharmonicity limit. A new self—consistent approach is formulated in terms of the Landau theory of phase transitions to account for zero—point and thermal fluctuations in anharmonic itinerant magnets. The role of spin fluctuations and Fermi excitations in MnSi, Ni3Al and ZrZn2 is discussed using the inelastic neutron scattering experiments.

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.

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