Synthetic ferrimagnets with thermomagnetic switching

High magnetocaloric efficiency of a NiFe/NiCu/CoFe/MnIr multilayer in a small magnetic field

“…It has been shown [12, 14-17] that FM layers surrounding the PM (or weakly FM) spacer strongly affect its magnetization up to the spacer thickness of  20 nm [12].Here we report on our measurements of S M in Ni 80 Fe 20 /Ni 67 Cu 33 /Co 90 Cu 10 /Mn 80 Ir 20 stacks at T close to T c of the Ni 67 Cu 33 spacer between the FM layers, i.e., Ni 80 Fe 20 and Co 90 Fe 10 . Such a heterostructure system exhibits reconfigurations of the mutual orientation of FM magnetizations, M 1 and M 2 , under applying a field of H sw 20 Oe due to their exchange decoupling across the spacer above its T c [14][15][16][17]. Our evaluations of the MCE in FM/PM/FM structures anticipate a very high MCE, dT/dH2.0 K/kOe in bias fields of only a few tens of oersted [11].…”

“…It is also important that the T c of the spacer can be tunable by varying the spacer composition. For example, a diluted Ni x Cu 1-x alloy, whose T c depends almost linearly on the Ni concentration, is a good candidate as the spacer material [14][15][16][17]. Fig.1.…”

Magnetocaloric effect in ferromagnet/paramagnet multilayer structures

“…The temperature dependence of the exchange coupling between the fer romagnetic layers in such a system has been studied both theoretically and experimentally [7][8][9]. Thin films of Ni x Cu 1 -x alloys were used as "weak" ferro magnetic spacers.…”

“…If the direction of the magnetization of one fer romagnetic film is fixed, the change in the mutual ori entation of magnetizations in ferromagnets occurs at the applied magnetic field of the order of the bias field H ex [7][8][9]. At the applied magnetic field exceeding ⎯(H ex -H c /2), we have the parallel orientation of the magnetizations of the ferromagnets, whereas at the applied magnetic field lower than -(H ex + H c /2), the orientations are antiparallel (H c is the coercive field of the "free" film).…”

Broadband Metallic Absorber on a Non‐Planar Substrate

“…Among them, gold blacks, [ 1,2 ] chemically etched electroless Ni-P alloys, [ 3,4 ] and fi lms of carbon nanotubes, [5][6][7] are some well-known examples, but are either fragile, thick (tens to hundreds of microns), or substrate-specifi c. Recent efforts focused on plasmonic and metamaterial thin-fi lm absorbers. Composites consisting of noble metal nanoparticles embedded in a dielectric background [9][10][11] can be constructed as broadband absorbers, and the absorption band can span UV, visible, and near-infrared regions by tuning the components. Metamaterial thin-fi lm absorbers, which adopt the metal-insulator-metal confi guration with subwavelength patches, [12][13][14] were recently extended to be broadband [15][16][17] by using sophisticated schemes for tuning and blending resonant frequencies of individual resonating elements, but the bandwidth thus achieved is not remarkable due to the diffi culty in integrating as many resonators as required on the same substrate.The common rule for designing a broadband absorber is to suppress refl ection by providing an effi cient impedance matching mechanism between air and the absorptive material, and to block transmission by providing an effi cient light-trapping mechanism or by putting the thin absorptive material on a metal refl ector (ground plane).…”