Quantum wells based on magnetic-dipolar-mode oscillations in disk ferromagnetic particles

Abstract

PACS. 03.65.-w -Quantum mechanics. PACS. 85.35.Be -Quantum well devices (quantum dots, quantum wires, etc.). PACS. 76.50.+g -Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance.Abstract. -We show that magnetic-dipolar-mode oscillations in a normally magnetized ferromagnetic disk have typical atomic properties like discrete-energy levels. Because of the discreteenergy eigenstates of such oscillations resulting from structural confinement, one can describe the oscillating system as a collective motion of quasiparticles -the light magnons. We calculate the energy levels in a magnetic quantum well and the effective masses of the light magnons.Introduction. -Semiconductor quantum dots are manmade structures in which electrons are confined in all three spatial directions similar to the physical situation in atoms. As they show typical atomic properties like discrete-energy levels and shell structures, they are often referred to as artificial atoms [1]. This provides various implementations of solid-state systems based on semiconductor quantum dots. It is interesting that confinement phenomena for magnetic dipolar modes in a normally magnetized ferrite disk may also show typical atomic properties like discrete-energy levels. Such wave processes reveal very special behaviors of the geometrical effects. As a starting point for this statement, we call the reader's attention to the fundamental difference between the experimental absorption spectra for magnetostatic (MS) modes in the sphere-shaped [2] and the disk-shaped ferrite resonators [3]. The δ-functional character of the multiresonance spectra, that one can see in the case of a ferrite disk resonator, leads to the clear conclusion that the energy of a source of a DC bias magnetic field is absorbing "by portions" or discretely, in other words. On the contrary, the spectrum of a ferrite sphere does not show a series of sharp field-dependent resonances and is characterized by very few and much "spreading" absorption peaks.The MS-mode characterization in ferrite samples looks as a relatively straightforward and old problem in magnetism. Nevertheless, some aspects of such oscillations should be reconsidered in view of macroscopically quantized methods. In the last years, there has been a renewed interest in the high-frequency dynamic properties of finite-size magnetic structures. In a series of recent publications, confinement phenomena of high-frequency magnetization dynamics in magnetic particles have been the subject of much experimental and theoretical

Magnetic-Dipolar-Mode Oscillations for Near- And Far-Field Manipulation of Microwave Radiation

“…There are energy gap scales with the bias magnetic field at a given operating frequency. In paper [44], it was shown that because of the discrete energy eigenstates of MDM oscillations resulting from structural confinement in a ferrite disk, one can describe the oscillating system as collective motion of quasiparticles -the "light magnons".…”

Handedness of magnetic-dipolar modes in ferrite disks

“…Magnetic-dipolar-mode oscillations in a ferrite sample occupy an intermediate position between two wave processes: the "pure" electromagnetic waves and the exchange-interaction waves. So one might suppose that the light magnons [12] are not subjected to the classical relativistic treatment and, at the same time, the ("real", "heavy") magnon motion laws. Based on the scalar magnetic-dipolar wave function we are able to obtain the complete-set functional basis in the energy-eigenstate spectral problem [11,12].…”

“…So one might suppose that the light magnons [12] are not subjected to the classical relativistic treatment and, at the same time, the ("real", "heavy") magnon motion laws. Based on the scalar magnetic-dipolar wave function we are able to obtain the complete-set functional basis in the energy-eigenstate spectral problem [11,12]. To get this orthonormal functional basis we attracted neither the notion of the RF electric field, nor the notion of the RF magnetization field.…”

“…For MS-wave waveguide modes in ferrite samples the spectral problem was formulated in [11,12]. The setting of a problem was made for a monochromatic wave process ( , where µ t is the permeability tensor.…”

“…In a view of recent experiments of a microwave magnetoelectric (ME) effect [17], an interest in MS oscillating spectra of a normally magnetized ferrite disks was renewed. The macroscopically quantum analysis [11,12], being a new consideration of an old topic, touches upon fundamental aspects of the physics of MS oscillations and, hopefully, gives a clue to the microwave ME effect in ferrite particles. In microwaves, ferrite resonators with multi-resonance MS-wave oscillations may have characteristic sizes two-four orders less than the free-space EM wavelength at the same frequency and, at the same time, much more than the exchange-interaction wavelength.…”