Magnetic‐Pole Flip by Millimeter Wave

Abstract

sustainable data storage systems. [4] To further enhance the recording capacity, the magnetic particle size must be reduced. [5,6] However, as magnetic particles become smaller, the thermal stability of the magnetization decreases. In order to maintain the thermal stability, enlargement of the magnetic anisotropy is necessary. Consequently, current magnetic recording heads cannot write against the strong magnetic anisotropy (Figure S1, Supporting Information). This problem is called the "magnetic recording trilemma." [7-11] It is common for magnetic recording media, including hard disk drives and magnetic tapes. To resolve the trilemma problem, several types of recording methods have been proposed such as heat-assisted magnetic recording and microwave-assisted magnetic recording. In basic research, photo-induced phase transitions in magnetic materials are actively studied. [12-23] In the present study, we focus on epsilon iron oxide for two main reasons. It exhibits high-frequency millimeter wave absorption in a wide frequency range of 35-222 GHz due to the zero-field ferromagnetic resonance (Table S1, Supporting Information). Additionally, it can maintain spontaneous magnetization due to ferrimagnetism even with a single nanometer size

Efficient Brownian oscillators and nanoheaters based on gallium-doped ε-Fe2O3

“…All of the peaks can be readily indexed to metalsubstituted e-Fe 2 O 3 . 10,11,[25][26][27] the D TEM AE SD = 24.9 AE 15.0 nm (N = 400), as it should be expected; yet, it is clear that the NPs are individually dispersed in water. TEM images of the sample show NPs with spherical or ellipsoidal shape (Fig.…”

Terahertz Wave Absorption Property of all Mixed Organic–Inorganic Hybrid Perovskite Thin Film MA(Sn, Pb)(Br, I)3 Fabricated by Sequential Vacuum Evaporation Method

“…Transmission type THz-TDS was utilized to characterize the samples and elucidate their THz-wave absorption properties. ( Nakajima et al, 2008 ; Nakajima et al, 2009 ; Nakajima et al, 2016 ; Jung et al, 2018 ; Ohkoshi et al, 2020 ; Agulto et al, 2021 ; Fitzky et al, 2021 ). Transmittances of the samples were obtained by non-destructive testing and analysis using an Advantest TAS7500 THz spectroscopy system, which allowed the direct measurement of time-domain THz waveforms and the corresponding power spectra at room temperature (22 ± 1°C) and dry air (relative humidity <1.5%) conditions.…”

Resonance Frequency Tuning of a 200 GHz Band Absorber by an External Magnetic Field

“…Epsilon iron oxide (ε‐Fe 2 O 3 ) nanomagnets are attractive because they have been reported to exhibit a large coercive field and high‐frequency millimeter‐wave absorption at 182 GHz by zero‐field ferromagnetic resonance (the so‐called natural resonance). [ 17–48 ] Metal‐substituted epsilon iron oxide (ε‐ M x Fe 2− x O 3 : M = Al 3+ , Ga 3+ , and In 3+ ) and Ti 4+ −Co 2+ cosubstituted series, ε‐(TiCo) x Fe 2− x O 3 , exhibit zero‐field ferromagnetic resonance over a wide frequency range of 35–182 GHz. Rhodium‐substituted epsilon iron oxide, ε‐Rh x Fe 2− x O 3 , shows even higher resonance frequencies above 182 GHz by increasing the Rh/Fe ratio.…”