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

Abstract

ε-GaxFe2−xO3 nanoparticles with huge coercivity and moderate magnetization can be useful in both mechanical and heating wireless magnetic actuation due to their low tendency to agglomerate.

Particle size effect on millimeter-wave absorption, rotation, and ellipticity of gallium-substituted epsilon iron oxide

“…They exhibit large magnetic anisotropy and high-frequency millimeter-wave absorption. 18–45 Additionally, metal-substituted epsilon iron oxide, ε-M x Fe 2− x O 3 , 46–70 exhibits millimeter-wave absorption in the range of 35–222 GHz, in which the resonance frequency is controlled by a kind of substitution metal and substitution ratio. Recently, the resonance frequency shift due to change on the particle size of ε-Fe 2 O 3 nanomagnets has been also reported.…”

Facile synthesis of epsilon iron oxides via spray drying for millimeter-wave absorption

“…7,8 The substitution of nonmagnetic elements with Fe sites enables tunable absorption in the millimeter-wave region (30-300 GHz). [8][9][10] Thus, several studies have been conducted to produce highpurity e-Fe 2 O 3 . The e-phase can be obtained in nanoparticle (NP) form rather than bulk form because it is an intermediate between g-Fe 2 O 3 and a-Fe 2 O 3 .…”

“…These findings are in accordance with those of previous studies, demonstrating that nonmagnetic substitution changes the magnetocrystalline anisotropy, resulting in tunable ferromagnetic resonance characteristics. [7][8][9][10] The corresponding permeability and permittivity values of the e-Ga x Fe 2Àx O 3 composite film are presented in Fig. 3…”

“…7,8 The substitution of nonmagnetic elements with Fe sites enables tunable absorption in the millimeter-wave region (30–300 GHz). 8–10…”

“…7,8 In particular, nonmagnetic substitution of Fe enables the adjustment of the coercivities of ε-Fe 2 O 3 , 20,21 resulting in tunable ferromagnetic resonance from 30 GHz to 230 GHz. 9,10 Thus, to provide a proof-of-concept of the millimeter-wave absorber, we prepared Ga-substituted ε-Fe 2 O 3 (ε-Ga x Fe 2− x O 3 , 0.24 ≤ x ≤ 0.48) via a spray drying method. All magnetic oxides formed a high-purity ε-phase, as shown in the XRD patterns in Fig.…”