scholarly journals Bi-reflection of spin waves

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Tomosato Hioki ◽  
Yusuke Hashimoto ◽  
Eiji Saitoh
Keyword(s):  
Spin Wave ◽  
Elastic Waves ◽  
Light Wave ◽  
Incident Angle ◽  
Spin Waves ◽  
Time Resolved ◽  
Reflected Light ◽  
Sample Edge ◽  
Out Of Plane ◽  
Angle Of Reflection

Abstract When a light wave is refracted at a boundary between two different media, it may split into two rays due to optical anisotropy, a phenomenon called birefringence. On the other hand, for a reflected light wave in an ordinary medium, the angle of reflection is always the same as the incident angle as expected from the law of reflection. Here, we report the observation of a split of reflected spin-waves, or bi-reflection of spin-waves, where a spin-wave refers to a wavy motion of electron spins in a magnetic material. We measured the spin-wave propagation in a magnetic garnet Lu2Bi1Fe3.4Ga1.6O12 by using time-resolved magneto-optical microscopy and found that the spin-wave splits in two as a result of reflection at the sample edge of an out-of-plane magnetized film. Systematic measurements combined with calculations unveiled that the bi-reflection is due to the hybridization with elastic waves.

scholarly journals The angular dependence of magnetization dynamics induced by a GHz range strain pulse

2022 ◽  
Author(s):  
Kakeru Tojo ◽  
Akira NAGAKUBO ◽  
Hirotsugu OGI
Keyword(s):  
Magnetic Field ◽  
Angular Dependence ◽  
Spin Wave ◽  
Echo Signal ◽  
Magnetization Dynamics ◽  
Time Resolved ◽  
Wave Resonance ◽  
Out Of Plane ◽  
Magneto Optical Kerr Effect ◽  
Strain Pulse

Abstract The dynamics of magnetization is important in spintronics, where the coupling between phonon and magnon attracts much attention. In this work, we study the angular dependence of the coupling between longitudinal-wave phonon and magnon. We investigated the magnetization dynamics using the time-resolved magneto-optical Kerr effect, which allows measuring spin-wave resonances and the magnetic echo signal. The frequency, mode number, and amplitude of the spin-wave resonance change with the out-of-plane angle of the external magnetic field. The amplitude of the magnetic echo signal caused by the strain pulse also changes with the angle. We calculate these angular dependences based on the Landau-Lifshitz-Gilbert equation and find that the angles of the external field and magnetic moment are important factors for the phonon-magnon coupling when phonon propagates in the thickness direction under the out-of-plane magnetic field.

scholarly journals Giant nonreciprocal emission of spin waves in Ta/Py bilayers

2016 ◽  
Vol 2 (7) ◽  
pp. e1501892 ◽  
Author(s):  
Jae Hyun Kwon ◽  
Jungbum Yoon ◽  
Praveen Deorani ◽  
Jong Min Lee ◽  
Jaivardhan Sinha ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Magnetic Materials ◽  
Spin Wave ◽  
Spin Waves ◽  
Logic Gates ◽  
Microwave Devices ◽  
Magnetization Direction ◽  
Spin Pumping ◽  
Plane Anisotropy ◽  
Out Of Plane

Spin waves are propagating disturbances in the magnetization of magnetic materials. One of their interesting properties is nonreciprocity, exhibiting that their amplitude depends on the magnetization direction. Nonreciprocity in spin waves is of great interest in both fundamental science and applications because it offers an extra knob to control the flow of waves for the technological fields of logics and switch applications. We show a high nonreciprocity in spin waves from Ta/Py bilayer systems with out-of-plane magnetic fields. The nonreciprocity depends on the thickness of Ta underlayer, which is found to induce an interfacial anisotropy. The origin of observed high nonreciprocity is twofold: different polarities of the in-plane magnetization due to different angles of canted out-of-plane anisotropy and the spin pumping effect at the Ta/Py interface. Our findings provide an opportunity to engineer highly efficient, nonreciprocal spin wave–based applications, such as nonreciprocal microwave devices, magnonic logic gates, and information transports.

MAGNONS TRANSMISSION THROUGH AN ATOMIC WIRE CONNECTING TWO ULTRATHIN HEISENBERG FERROMAGNETS

2009 ◽  
Vol 16 (01) ◽  
pp. 55-63
Author(s):  
M. BELHADI ◽  
A. KHATER
Keyword(s):  
Spin Wave ◽  
Incident Angle ◽  
Spin Waves ◽  
Molecular Wires ◽  
Atomic Scale ◽  
Linear Molecule ◽  
Dimensionless Frequency ◽  
Fano Resonances ◽  
Ferromagnetic Films ◽  
Coherent Reflection

The magnons transport properties of molecular wires connecting two Heisenberg ferromagnets are studied within the framework of the matching method and with use of a realistic atomic structure. The model system consists of two nanostructured ferromagnetic films on either side of the junction and the atomic wire consists of a linear molecule connecting two ultrathin solid ferromagnetic films. A theoretical model is presented for the study of the transmission and the reflection of spin waves at the atomic wire junction. The calculation was made at the atomic scale for two identical waveguides with ordered spins and coupled by Heisenberg exchange interaction between first neighbors. Our analysis yields a detailed understanding of the spin-wave coherent scattering at the linear molecular junction. We calculate, in particular, the coherent reflection R and transmission T coefficients, which constitute the elements of the scattering matrix in accordance with the Landauer–Büttiker scattering formalism, as well as the magnon transmittance of the atomic wire for spin-waves incident from the interior of the film on the junction. The most representative numerical results obtained for the system of two slabs made up of three Fe ferromagnetic atomic layers connected with an Fe or Gd atomic wire are presented as function of the dimensionless frequency Ω in the magnons energy band. The coherent reflection and transmission scattering cross sections show characteristic spectral features, depending on the length of the wire, on the cut-off frequencies for the propagating magnons, as well as on the magnons incidence angle. The results illustrate the occurrence of Fano resonances in the transmitted spectra due to the interaction of localized spin states on the atomic wire with the propagating spin waves of the waveguide. An interesting physical effect is observed for this magnetic atomic junction, namely the frequency selective conductance of the spin waves via Fano resonances, by an appropriate choice of the spin-wave incident angle.

SPIN WAVES TRANSMISSION VIA A MOLECULAR JUNCTION CONNECTING TWO QUASI-2D HEISENBERG FERROMAGNETS

2009 ◽  
Vol 08 (06) ◽  
pp. 557-564
Author(s):  
M. BELHADI ◽  
N. AIDER ◽  
A. KHATER
Keyword(s):  
Spin Wave ◽  
Spin Fluctuation ◽  
Incidence Angle ◽  
Incident Angle ◽  
Spin Waves ◽  
Molecular Junction ◽  
Mathematical Framework ◽  
Fano Resonances ◽  
Magnetic Exchange ◽  
System Parameters

A theoretical investigation of spin wave dynamics and scattering at a molecular junction between two Heisenberg ferromagnets is presented. The model system consists of two ferromagnetic ultrathin films with equal thickness of three atomic layers, joined together by a magnetic molecule. No electronic effects are considered, but local changes in the magnetic exchange field are assumed to be dominant. The mathematical framework of the matching method is used with nearest neighbor magnetic exchange interactions, to analyze both the spin fluctuation dynamics and the spin wave scattering phenomena at the junction boundary. The coherent reflection and transmission probabilities and the conductance of spin waves incident from the interior of the films onto the boundary are calculated in accordance with the Landauer–Büttiker formalism, and numerical results are presented for representative sets of system parameters for a large range of scattering frequencies. The scattered spectra show interesting sharp features, with associated Fano resonances, as a function of scattering frequencies, system parameters, and spin wave incidence angle. Moreover, a frequency selective conductance of the spin waves via Fano resonances can be obtained by an appropriate choice of the spin wave incident angle and system parameters.

scholarly journals The investigation of Neutron Scattering In Spin Waves Theory of Ferromagnetic Crystals

2014 ◽  
Vol 8 (4) ◽  
Author(s):  
Azadeh Farzaneh ◽  
Mohammad Reza Abdi ◽  
Khadije Rezaee Ebrahim Saraee
Keyword(s):  
Neutron Scattering ◽  
Spin Wave ◽  
Cross Section ◽  
Inelastic Neutron Scattering ◽  
Spin Waves ◽  
Wave Theory ◽  
Spin Correlation ◽  
Inelastic Neutron ◽  
Magnetic Behaviour ◽  
Spin Interaction

Inelastic neutron scattering, probing the temporal spin-spin correlation at the different microscopic scale, is a powerful technique to study the magnetic behaviour of ferromagnetic crystals. In addition, high penetration power of neutron in samples has made it as a useful way for spin-spin interaction in neutron scattering. Changes in the magnetic cross section in term of different energy transfer and temperatures are calculated for nickel and iron as transition metals in Heisenberg model versus spin wave theory by considering atomic form factor. Finally, the effect of magnetic structure and behaviour of crystal in measuring cross-section shows that increasing temperature results in the Cross-section increase Also, the existence of propagating spin waves below Tc is compared in Ni and Fe in different momentum transfers. The relation of spin wave energy with temperature dependence of nickel has created different behaviour in the changes of cross section rather than iron.

Spin-Wave Dynamics in Antiferromagnets under Electric Current

2021 ◽  
Vol 1 ◽  
Keyword(s):  
Electric Current ◽  
Spin Wave ◽  
Doppler Effect ◽  
Spin Waves ◽  
Microscopic Analysis ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Wave Dynamics

Electric current causes a Doppler effect in spin waves in ferromagnets through a spin-transfer torque. We report that antiferromagnets allow two such spin-transfer torques and present a microscopic analysis that interpolates ferro- and antiferromagnetic transport regimes.

The theory of the ferromagnetism of conduction electrons at low temperatures

1965 ◽  
Vol 284 (1398) ◽  
pp. 423-441 ◽  
Keyword(s):  
Low Temperature ◽  
Spin Wave ◽  
Single Particle ◽  
Lattice Site ◽  
Spontaneous Magnetization ◽  
Spin Waves ◽  
Green Functions ◽  
Linear Combinations ◽  
Conduction Electrons ◽  
Occupation Numbers

A theory is presented in which the effect of spin waves on the single-particle states of conduction electrons is obtained as well as the effect of the conduction electrons on the spin waves. Green function techniques are employed. The Hamiltonian is taken to contain the single-particle energies of the conduction electrons in the absence of interactions, the Coulomb interaction between electrons in Wannier states centred on the same lattice site C , and the interatomic exchange terms J ij . Interband integrals are neglected. The chain of equations for the single-particle Green functions is decoupled in such a way as to include the effects of the spin waves in the single-particle Green functions. The theory is worked out on the assumption that C is very much greater than the band width and the J ij so that at T ═ 0 the double occupation of Wannier orbital states is the minimum possible. The resulting single-particle occupation numbers are linear combinations of Fermi-Dirac functions. The low temperature spontaneous magnetization ξ is found to be a product of a spin-wave magnetization and a single-particle magnetization ξ s.p ., and so contains terms varying as T 1 and T 1 , and T 2 if both spin sub-bands are partially occupied in the ground state. The low temperature specific heat contains T and T 1 terms. The results of the Heisenberg model are obtained in the appropriate limit. Expressions for the spin-wave energy and its temperature dependence are discussed.

Improvement of Micro-PIV Resolution by Selective Seeding

2006 ◽  
Author(s):  
Michal M. Mielnik ◽  
Lars R. Sætran
Keyword(s):  
Optical Measurement ◽  
Fluid Layer ◽  
Field Measurements ◽  
Time Resolved ◽  
Micro Piv ◽  
Tracer Particles ◽  
Seeding Method ◽  
Image Velocimetry ◽  
Out Of Plane ◽  
Measurement Depth

A novel seeding method, permitting high out-of-plane resolution and instantaneous (time-resolved) velocity field measurements using a standard Microscale Particle Image Velocimetry (micro-PIV) setup, is presented. The method relies on selective seeding of a thin fluid layer within an otherwise particle-free flow. The generated particle sheet defines the depth and position of the measurement plane, independently of the details of the optical setup. Therefore, for low magnification objectives in particular, considerable improvement in the measurement depth is possible. Selectively seeded micro-PIV (SeS-PIV) is applied to a microchannel flow, and the measured instantaneous velocity fields are in excellent agreement with the theoretical solution for the flowfield. The currently presented measurements have a depth-wise resolution 20% below the estimated optical measurement depth of the micro-PIV system. In principle, a measurement depth corresponding to the diameter of the tracer particles may be achieved.

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