High-speed characterization of submicrometer giant magnetoresistive devices

A microwave test structure has been designed to measure the high-speed resp onse of giant magnetoresistive (GMR) devices. The test structure uses micro wave transmission lines for both writing and sensing the devices. Pseudo-sp in-valve devices, with line widths between 0.4 and 0.8 mm, were successfull y switched with pulses whose full width at half-maximum was 0.5 ns. For sma ll pulse widths tau(pw) the switching fields are observed to increase linea rly with 1/tau(pw). The increase in switching fields at short pulse widths is characterized by a slope which, for the current devices, varies between 4 and 16 mu A s/m (50-200 Oe ns). The magnetoresistive response during rota tion and switching was observed. For small rotations (similar to 45 degrees between layer magnetizations) the GMR response pulses had widths of 0.46 n s, which is at the bandwidth limit of our electronics. For larger rotations (similar to 90 degrees) the response pulses broadened considerably as the magnetic layers were rotated near the unstable equilibrium point perpendicu lar to the device axis. Full 180 degrees switches of both soft and hard lay ers were observed with switching times of approximately 0.5 ns. (C) 1999 Am erican Institute of Physics. [S0021-8979(99)70308-7].