Thick barium ferrite films use for passive isolators

Abstract

PACS 75.50.Gg, 75.60Nt, 75.70Ak Ferrites have magnetic properties suitable for electronic applications, especially in the microwave range (circulators and isolators). Hexagonal ferrite, such as barium ferrite, are of great interest for microwave device applications because of their large resistivity and high permeability at high frequencies. BaM films are deposited under optimized conditions by RF magnetron sputtering on alumina substrates. In order to crystallize the films that are amorphous after deposition, a post deposition annealing at 800 °C is implemented. All samples present a good crystallization, a smooth surface and a good in-depth uniformity. The magnetic properties of BaM films show an optimized coercive force and saturation magnetization of 330 kA/m and 500 mT respectively. These values are close to that of the bulk BaM. Isolators are then realized and measured by a vector network analyzer and a probing system. Results on transmission coefficients show a non reciprocal effect, which reaches 8.3 dB/cm at 50 GHz. This proves that such a component behaves like an isolator in the 50 GHz band.

M-Type Barium Hexagonal Ferrite Films

“…10,[18][19][20][21][22][23][24] Such devices include (1) notch filters made of BaM thin films and microstrip geometry, (2) notch filters made of BaM slabs and strip-line geometry, (3) selfbiased notch filters using high-M r BaM thin films and coplanar waveguide (CPW) geometry, (4) notch filters based on the excitation of confined magnetostatic waves in narrow BaM strips and CPW configurations, and (5) phase shifters using BaM thin films and CPW geometry. This section describes the device configurations and responses of (3), (4), and (5).…”

“…Emphasis has been placed on the optimization of deposition processes for low-loss, self-biased BaM thin films, 7,8,9,10 the deposition of BaM thin films on "non-conventional" substrates, such as semiconductor substrates 11,12,13,14 and metallic substrates, 15 the fabrication of BaM thick films on semiconductor substrates, 16,17 the demonstration of BaM-based planar mm-wave devices, 18,19,20,21,22,23,10,24 the development of BaM-based ferromagnetic/ferroelectric heterostructures, 25,26,27,28,29 and the study of multiferroic effects in single-phase BaM materials. 30 A variety of different techniques have been used to fabricate BaM film materials.…”

“…30 A variety of different techniques have been used to fabricate BaM film materials. These include pulsed laser deposition (PLD), 7,8,9,10,11,12,28,31 liquid phase epitaxy (LPE), 32,33,34,35 RF magnetron sputtering, 36,37,19,38,39,40 molecular beam epitaxy (MBE), 14 metallo-organic decomposition (MOD), 15 chemical vapor deposition (CVD), 41 and screen printing. 16,17 The device demonstration includes both numerical 20,21,22 and experimental efforts.…”

“…18,21,22,23,10,24 The devices demonstrated include phase shifters, 21 filters, 22,23,10 ,24 circulators, 18 and isolators. 19 This chapter reviews the main advances made in the field of BaM materials and devices over the past five years. Section 2 gives a brief introduction to hexagonal ferrites first and then describes in detail the structure and properties of BaM materials.…”