scholarly journals Quadrupole Excitation in Tunnel Splitting Oscillation in Nanoparticle

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
Yousef Yousefi ◽  
Khikmat Kh. Muminov
Keyword(s):  
Magnetic Field ◽  
Spin System ◽  
Easy Axis ◽  
Second Order ◽  
Transverse Anisotropy ◽  
Quadrupole Excitation ◽  
Tunnel Splitting

We analyze the interference between tunneling paths that occur for a spin system with special Hamiltonian both for dipole and quadrupole excitations. Using an instanton approach, we find that as the strength of the second-order transverse anisotropy is increased, the tunnel splitting for both excitations is modulated, with zeros occurring periodically and the number of quenching points for quadrupole excitation decreasing. This effect results from the interference of four tunneling paths connecting easy-axis spin orientations and occurs in the absence of any magnetic field.

FIRST- AND SECOND-ORDER CROSSOVERS OF SPIN TUNNELING IN Mn12-ACETATE MOLECULAR MAGNET WITH FOURTH-ORDER ANISOTROPY

2002 ◽  
Vol 16 (15n16) ◽  
pp. 555-567
Author(s):  
CHANG-SOO PARK
Keyword(s):  
Perturbation Theory ◽  
External Field ◽  
Fourth Order ◽  
Easy Axis ◽  
Second Order ◽  
Molecular Magnet ◽  
Crossover Temperature ◽  
Transverse Anisotropy ◽  
First Order ◽  
Spin Tunneling

We have studied the escape rate of spin tunneling in a molecular magnet with a fourfold easy axis, such as Mn 12-acetate, in the presence of an external field applied perpendicular to the easy axis. Both perturbation theory and numerical diagonalization have been used to investigate the type of quantum-classical crossover and the crossover temperature T c . We have observed that T c ~ 1.2 K which agrees with experimental results,9 and the first-order region increases due to the fourth-order transverse anisotropy. More interestingly, when the field is applied along the hard axis, first- and second-order regions alternate as the field increases.

scholarly journals Magnetic-field induced quantum phase transition and critical behavior in a gapped spin system

2007 ◽  
Vol 310 (2) ◽  
pp. 1352-1354 ◽  
Author(s):  
F. Yamada ◽  
T. Ono ◽  
M. Fujisawa ◽  
H. Tanaka ◽  
T. Sakakibara
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Quantum Phase Transition ◽  
Spin System ◽  
Critical Behavior ◽  
Quantum Phase

scholarly journals Reversibility of the Magnetocaloric Effect in the Bean-Rodbell Model

2021 ◽  
Vol 7 (5) ◽  
pp. 60
Author(s):  
Luis M. Moreno-Ramírez ◽  
Victorino Franco
Keyword(s):  
Magnetic Field ◽  
Thermal Hysteresis ◽  
Entropy Change ◽  
Second Order ◽  
Zero Field ◽  
First Order ◽  
Magnetic Field Change ◽  
Magnetocaloric Materials ◽  
Moderate Magnetic Field ◽  
The Magnetic Field

The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.

scholarly journals Magnetic Domain Transition of Adjacent Narrow Thin Film Strips with Inclined Uniaxial Magnetic Anisotropy

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 279
Author(s):  
Tomoo Nakai
Keyword(s):  
Magnetic Field ◽  
Easy Axis ◽  
Magnetic Domain ◽  
Magnetic Interaction ◽  
Individual Element ◽  
Typical Characteristic ◽  
Many Body ◽  
Uniaxial Magnetic Anisotropy ◽  
Line Arrangement ◽  
Normal Magnetic Field

This study deals a phenomenon of magnetic domain transition for the stepped magneto-impedance element. Our previous research shows that an element with 70° inclined easy axis has a typical characteristic of the domain transition, and the transition can be controlled by the normal magnetic field. In this paper, we apply this phenomenon and controlling method to the line arrangement adjacent to many body elements, in which mutual magnetic interaction exists. The result shows that the hidden inclined Landau–Lifshitz domain appears by applying a distributed normal field the same as an individual element.

Ein Level-Crossing-Experiment im angeregten (5p1/2 5d5/2)J=2-Term des Sn I zur Untersuchung der Energieverschiebungen im elektrischen Feld / Level-Crossing Experiment in the Excited (5p1/25d5/2)J=2-State of the Sn I for the Investigation of the Energy Shifts in an Electric Field

1970 ◽  
Vol 25 (5) ◽  
pp. 608-611
Author(s):  
P. Zimmermann
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Stark Effect ◽  
Second Order ◽  
Wave Functions ◽  
Zero Field ◽  
Homogeneous Electric Field ◽  
Level Crossing ◽  
Crossing Experiment ◽  
The Magnetic Field

Observing the change of the Hanle effect under the influence of a homogeneous electric field E the Stark effect of the (5p1/25d5/2)j=2-state in Sn I was studied. Due to the tensorial part β Jz2E2 in the Hamiltonian of the second order Stark effect the signal of the zero field crossing (M ∓ 2, M′ = 0 β ≷ 0 ) is shifted to the magnetic field H with gJμBH=2 | β | E2. From these shifts for different electric field strengths the value of the Stark parameter|β| = 0.21(2) MHz/(kV/cm)2 · gJ/1.13was deduced. A theoretical value of ß using Coulomb wave functions is discussed.

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