Influence of antiferromagnetic interlayer exchange interactions in a double ferromagnetic film on the hysteresis curve

The Monte Carlo replica algorithm studies of phase transitions and critical phenomenaofthe layered triangular antiferromagnetic Ising model withvariable interlayer exchange interaction. Investigations were carried out for the ratios of the value of the intralayerJ1 and interlayer J2 exchange interactions in the range of values r = J2 / J1 = 0.01 ÷ 1.0. It was found that in the above range r is observed second-order phase transition.Static critical exponents for the heat capacityα, susceptibility γ, order parameter β, correlation radius ν, and the Fisher exponent ηare computed by means of the finite-size scaling theory. It is shown that the universality class of the critical behavior of the model is maintained in the range of 0.05 <r≤1.0.The results obtained suggest that3D frustrated Ising models on stacked triangularlattice with interlayer-to-intralayer exchange ratio 0.05<r≤1.0. preserves the universality class of criticalbehavior. At lower r, a crossover from 3D to 2D criticalbehavior is observed.

Download Full-text

Обменные взаимодействия в гетероструктурах NiFe/Ta/IrMn в условиях дефицита Ta

Физика твердого тела ◽

10.21883/ftt.2020.06.49348.647 ◽

2020 ◽

Vol 62 (6) ◽

pp. 915

Author(s):

Р.Б. Моргунов ◽

А.Д. Таланцев ◽

М.В. Бахметьев ◽

Н.В. Грановский

Keyword(s):

Exchange Bias ◽

Exchange Interactions ◽

Contact Exchange ◽

Conduction Electrons ◽

Ferromagnetic Layers ◽

Temperature Dependences ◽

Interlayer Exchange ◽

First Contact

In the NiFe/Ta/IrMn structures, the contributions of two types of exchange interactions are separated at the NiFe/IrMn interface, partially separated by non-magnetic Ta fragments. The first “contact” exchange corresponds to the NiFe/IrMn fragments. The second “interlayer” exchange is provided by the Ta conduction electrons in the NiFe/Ta/IrMn fragments. A comparison of the temperature dependences of the exchange bias in heterostructures with varied Ta spacer at fixed parameters of the ferromagnetic layers allowed us to separate the contributions of the above types of exchange interactions and to establish their temperature dependences. The energies of the exchange interactions in the NiFe/IrMn and NiFe/Ta/IrMn fragments were determined.

Download Full-text

Strain Induced Anisotropic Magnetic Behaviour and Exchange Coupling Effect in Fe-SmCo5 Permanent Magnets Generated by High Pressure Torsion

Crystals ◽

10.3390/cryst10111026 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1026

Author(s):

Lukas Weissitsch ◽

Martin Stückler ◽

Stefan Wurster ◽

Peter Knoll ◽

Heinz Krenn ◽

...

Keyword(s):

High Pressure ◽

Permanent Magnets ◽

Elevated Temperatures ◽

High Pressure Torsion ◽

Coupling Effect ◽

Exchange Interactions ◽

Hysteresis Curve ◽

Chemical Compositions ◽

Squid Magnetometry ◽

Nano Structure

High-pressure torsion (HPT), a technique of severe plastic deformation (SPD), is shown as a promising processing method for exchange-spring magnetic materials in bulk form. Powder mixtures of Fe and SmCo5 are consolidated and deformed by HPT exhibiting sample dimensions of several millimetres, being essential for bulky magnetic applications. The structural evolution during HPT deformation of Fe-SmCo5 compounds at room- and elevated- temperatures of chemical compositions consisting of 87, 47, 24 and 10 wt.% Fe is studied and microstructurally analysed. Electron microscopy and synchrotron X-ray diffraction reveal a dual-phase nanostructured composite for the as-deformed samples with grain refinement after HPT deformation. SQUID magnetometry measurements show hysteresis curves of an exchange coupled nanocomposite at room temperature, while for low temperatures a decoupling of Fe and SmCo5 is observed. Furthermore, exchange interactions between the hard- and soft-magnetic phase can explain a shift of the hysteresis curve. Strong emphasis is devoted to the correlation between the magnetic properties and the evolving nano-structure during HPT deformation, which is conducted for a 1:1 composition ratio of Fe to SmCo5. SQUID magnetometry measurements show an increasing saturation magnetisation for increasing strain γ and a maximum of the coercive field strength at a shear strain of γ = 75.

Download Full-text

Interlayer exchange interactions,SU(4)soft waves, and skyrmions in bilayer quantum Hall ferromagnets

Physical Review B ◽

10.1103/physrevb.65.075311 ◽

2002 ◽

Vol 65 (7) ◽

Cited By ~ 24

Author(s):

Z. F. Ezawa ◽

K. Hasebe

Keyword(s):

Quantum Hall ◽

Exchange Interactions ◽

Interlayer Exchange ◽

Bilayer Quantum Hall

Download Full-text

Магнитные структуры и магнитные фазовые переходы в редкоземельных интерметаллидах RMn-=SUB=-2-=/SUB=-Si-=SUB=-2-=/SUB=- (R=Sm, Tb)

Физика твердого тела ◽

10.21883/ftt.2018.06.45979.03m ◽

2018 ◽

Vol 60 (6) ◽

pp. 1071

Author(s):

Н.В. Мушников ◽

Е.Г. Герасимов ◽

В.С. Гавико ◽

П.Б. Терентьев ◽

К.А. Язовских ◽

...

Keyword(s):

Magnetic Anisotropy ◽

Magnetic Order ◽

Magnetic Measurements ◽

Exchange Interactions ◽

Layered Compounds ◽

Rare Earth Atom ◽

Magnetic Structures ◽

Range Magnetic Order ◽

Interlayer Exchange ◽

Long Range Magnetic Order

AbstractThe magnetic structures that form in La_1– x R_ x Mn_2Si_2 ( R = Sm, Tb) layered compounds with various concentrations x have been determined by magnetic neutron diffraction and magnetic measurements, and the magnetic phase diagrams have been built. It is shown that the formation of the magnetic structures is dependent not only on exchange interactions, but also on the type of the magnetic anisotropy of a rare-earth atom. It is found that, in La_1– x Tb_ x Mn_2Si_2 compounds with 0.2 < x < 0.5, the competition of the Tb–Mn and Mn–Mn interlayer exchange interactions and the existence of a strong uniaxial magnetic anisotropy in the Mn and Tb sublattices leads to the frustrated magnetic state and prevents the formation of the long-range magnetic order in the Tb sublattice.

Download Full-text