Integrated self-biased hexaferrite microstrip circulators for millimeter-wavelength applications

Recent advances in processing and applications of microwave ferrites

“…In 1992, a textured barium/strontium ferrite with remanent magnetization of 3.5 kG and uniaxial anisotropy field of 21 kOe was utilized by Zeina et al to design microstrip and stripline circulators operating at 37 and 32 GHz, respectively [114]. In 2001, an integrated self-biased microstrip circulator was fabricated by Oliver et al through bonding of textured SrM platelets to silicon substrates in a low-temperature process compatible with semiconductor fabrication requirements [115]. Insertion loss of 2.8 dB and isolation of 33 dB were measured at 28.9 GHz with a 20 dB bandwidth of 1%.…”

In-plane c-axis oriented barium hexaferrite films prepared by magnetron sputtering

“…M-type barium hexaferrite (BaM) films are promising candidates for next-generation microwave medium materials due to their selfbiasing behavior and high operation frequency [1][2][3][4][5][6]. In-plane caxis aligned (IPCA) BaM films have gained special attention over the past decade due to various favorable properties such as ease to achieve higher remanence ratio and high operation frequency at low bias fields [7].…”

Magnetic and microwave magnetic properties of barium hexaferrite permanent magnet films having the c-axis in the film plane

“…It is this dual functionality that allows one to apply hexaferrite materials in devices at frequencies that are inaccessible to traditional microwave ferrites. 1,2 The large uniaxial anisotropy present in barium hexaferrite (BaFe 12 O 19 ) is coincident with the c-axis of the hexagonal unit cell, such that the easy axis of the magnetization lies along the ͓0001͔ direction. In general, different types of microwave devices have different operational requirements with respect to the orientation of the ferrite magnetization vector and the microwave propagation vector.…”