Preparation of all-oxide ferromagnetic/ferroelectric/ superconducting heterostructures for advanced microwave applications

Abstract

As candidates for functional layers, 3d transition metal oxides with perovskite structures show some interesting properties, such as ferromagnetism, ferroelectricity and superconductivity. Accordingly, combinations of these properties can be used to create new tunable microwave devices. Ferromagnetic/ferroelectric/superconducting multistructures, such as La0.70Sr0.30MnO3 (LSMO)/Pb(Zr0.52Ti0.48)O3 (PZT)/YBa2Cu3O7-y (YBCO) and YBCO/PZT/LSMO, have been fabricated by ArF excimer laser deposition on LaSrGaO4 (LSGO) [001] and (La0.30Sr0.70)(Al0.65Ta0.35)O3 (LSAT) [001] substrates. The resulting trilayer films have a highly c-axis oriented structure. Epitaxial YBCO films formed on PZT/LSMO//LSAT have a zero-resistance temperature of 87 K. Moreover, D-E and M-H hysteresis loop are observed for the LSMO/PZT/YBCO//LSGO structure using a conventional Sawyer-Tower circuit and a superconducting quantum interference device (SQUID). The remanent polarization and coercive field of the PZT layer are found to be 19 µC cm-2 and 275 kV cm-1 at 70 K, respectively. The remanent magnetic moment and coercive magnetic field are about 2.6 µB/site and 50 Oe respectively at 78 K. Furthermore, the microwave surface resistance (RS) (22 GHz) of the YBCO film in the YBCO/PZT/LSMO structure was 1.32 m at 77 K. These results suggest that LSMO/PZT/YBCO structures are favourable for use in superconducting microwave applications such as tunable phaseshifters and filters.

The homogenized equations of motion for an activated elastic lamination in plane strain

“…Taking the relevant derivatives produces a new expression for Eq. (37), 4 M eff can be interpreted as a tensor of effective (or attached) masses. This concept shows up in hydrodynamics [2].…”

“…There are many examples of materials with properties that are time variable: muscle fiber, ferroelectrics/ferromagnetics, LC-circuits, etc. Recent advancements in material science and technology have shown that material parameters such as dielectric permittivity and magnetic permeability [4,13], or even elasticity and mass density [5,6], can be changed both in space and in time. The rate at which these changes can happen range from slow to very fast (e.g., at the flip of a switch).…”

Dynamic materials with formation of clots: optimal mass transport in one spatial dimension without takeover

“…Various means can be used to maintain the property patterns variable in space and time. In electromagnetic applications, such variability can be achieved by the network switching artificially implemented in both radio and optical frequency ranges [7,8]. In the traffic flow, the property pattern is not a material one: it is a velocity chart introduced by traffic regulations and implemented through the use of traditional signals, such as traffic lights and road signs, applied wherever and whenever necessary.…”

High frequency tunable LC devices with ferroelectric/ferromagnetic thin film heterostructure

“…Among various ferroelectric thin films, BST((Ba,Sr)TiO 3 ) thin film is the most attractive candidate for microwave and millimeter-wave frequency devices such as varactors, tunable filters, and tunable phase shifters because of high tunability (field-dependent change of dielectric constant) and low dielectric loss at microwave frequencies [2 -8]. On the other hand, tunable microwave filters and phase shifters utilizing epitaxial ferroelectric/ferromagnetic/superconducting thin films with perovskite structures have been proposed [9]. Because both C and L of a microwave device can be simultaneously changed in this heterostructure, the resonance frequency f r (= 1/2 LC π ) and phase velocity v p (= 1/ LC ) determined by the LC product are very large while maintaining the transmission line characteristic impedance Z 0 (= / L C) that is specially an important property for a phase shifter, resulting in the reduced insertion loss generated between the device and transmission line [9].…”

“…On the other hand, tunable microwave filters and phase shifters utilizing epitaxial ferroelectric/ferromagnetic/superconducting thin films with perovskite structures have been proposed [9]. Because both C and L of a microwave device can be simultaneously changed in this heterostructure, the resonance frequency f r (= 1/2 LC π ) and phase velocity v p (= 1/ LC ) determined by the LC product are very large while maintaining the transmission line characteristic impedance Z 0 (= / L C) that is specially an important property for a phase shifter, resulting in the reduced insertion loss generated between the device and transmission line [9]. Recently, there have been some preliminary reports on tunable microwave filters and phase shifters utilizing layered ferroelectricferromagnetic structure [10,11].…”