In-plane and out-of-plane anisotropic magnetoresistance in Ni80Fe20 thin films

The anisotropic magnetoresistance (AMR) has been measured for Ni80Fe20 thin films, with the magnetization vector rotating in the film plane as well as out of the film plane. The out-of-plane (OF) AMR is found to be considerably larger than the in-plane (IF) effect, and strongly dependent on the degree of texture. In untextured films, the difference between the IP- and the OP-AMR is explained in terms of a dimensionality effect, whereas in (111)-textured films an additional contribution to the OP-AMR is found

Magnetoresistance in Ni\u3csub\u3e80\u3c/sub\u3eFe\u3csub\u3e20\u3c/sub\u3e/Cu/Ni \u3csub\u3e80\u3c/sub\u3eFe\u3csub\u3e20\u3c/sub\u3e/Fe\u3csub\u3e50\u3c/sub\u3eMn\u3csub\u3e50\u3c/sub\u3e spin valves with low coercivity and ultrahigh sensitivity

\u3cp\u3eWe present magnetoresistance measurements on Ni\u3csub\u3e80\u3c/sub\u3eFe \u3csub\u3e20\u3c/sub\u3e/Cu/Ni\u3csub\u3e80\u3c/sub\u3eFe\u3csub\u3e20\u3c/sub\u3e/Fe\u3csub\u3e50\u3c/sub\u3eMn\u3csub\u3e50\u3c/sub\u3e spin valves with crossed anisotropies: the easy magnetization direction of the unbiased Ni\u3csub\u3e80\u3c/sub\u3eFe\u3csub\u3e20\u3c/sub\u3e layer is perpendicular to the exchange biasing field which effectively works on the second Ni\u3csub\u3e80\u3c/sub\u3eFe \u3csub\u3e20\u3c/sub\u3e layer due to the interaction with the Fe\u3csub\u3e50\u3c/sub\u3eMn \u3csub\u3e50\u3c/sub\u3e layer. The hysteresis in the low-field magnetoresistance is less than 0.03 kA/m, which is ten times smaller than the hysteresis for similar materials with parallel anisotropies. The sensitivity (∂R/R \u3csub\u3e∞\u3c/sub\u3e)/∂H ranges from 8% to 18%/(kA/m), depending on the preparational method. To our knowledge this combination of very high sensitivity and very low coercivity has not been reported before.\u3c/p\u3

Giant magnetoresistance and its application in recording heads

A short overview is given of the giant magnetoresistance (GMR) effect and its device applications. As an example of present research topics, the optimization of the ferromagnetic-layer composition of spin valves for application in recording heads is discussed. The influence on output voltage and stability has been investigated in test structures and compared with material parameters that were experimentally obtained from unpatterned films. It is found that in practical applications a small addition of cobalt is advantageous, since, although the output voltage is decreased, it leads to an improvement in reproducibility, linearity, signal-to-noise ratio and dynamic range

MEMS tunable capacitors and switches for RF applications

\u3cp\u3eRF MEMS capacitive switches and tunable capacitors have been realized in an industrialized thin-film process developed for manufacturing high-quality inductors and capacitors. Combining integrated passives with high-performance tuning and switching elements on the same die offers a potential for building a new generation of RF front-ends for hand-held mobile communication. Capacitive switches with an insertion loss of 0.4 dB and an isolation of 17 dB at 1 GHz have been demonstrated. Dual-gap relay type tunable capacitors have been fabricated that show a continuous and reversible tuning ratio of 12 together with a quality factor larger than 150 at frequencies higher than 0.5 GHz. These are the highest tuning ratio and quality factor reported to date. A 0-level packaging concept that is compatible with the fabrication technology has been adopted.\u3c/p\u3

Magnetic particles with perpendicular anisotropy for mechanical cancer cell destruction

We demonstrate the effectiveness of out-of-plane magnetized magnetic microdiscs for cancer treatment through mechanical cell disruption under an applied rotating magnetic field. The magnetic particles are synthetic antiferromagnets formed from a repeated motif of ultrathin CoFeB/Pt layers. In-vitro studies on glioma cells are used to compare the efficiency of the CoFeB/Pt microdiscs with Py vortex microdiscs. It is found that the CoFeB/Pt microdiscs are able to damage 62 ± 3% of cancer cells compared with 12 ± 2% after applying a 10 kOe rotating field for one minute. The torques applied by each type of particle are measured and are shown to match values predicted by a simple Stoner-Wohlfarth anisotropy model, giving maximum values of 20 fNm for the CoFeB/Pt and 75 fNm for the Py vortex particles. The symmetry of the anisotropy is argued to be more important than the magnitude of the torque in causing effective cell destruction in these experiments. This work shows how future magnetic particles can be successfully designed for applications requiring control of applied torques.This research was funded by NIH grant R01NS077388 ‘Magnetic Vortex Mixrodiscs for Glioma therapy’, the European Community under the Seventh Framework Program ERC contract No. 247368: 3SPIN, and the EPSRC Cambridge NanoDTC, EP/G037221/1