Structure and sensor properties of a robust GMR material system

Recently we have developed a robust GMR material system, based on an artificial antiferromagnet which is exchange-biased with Ir-Mn. By combining magnetoresistance and magnetization measurements with Transmission Electron Microscopy analyses we show that the degree of [111] texture has direct effects on the sensor properties of the GMR multilayer. The degree of texture turns out to depend not only on the buffer layer, but also on the thickness of the Ir-Mn layer. The strongest texture is found for Ir-Mn layer thicknesses of around 4 nm. For this thickness the largest exchange-biasing field and GMR ratio are also obtained (after cooling in a magnetic field), but the blocking temperature is significantly reduced. If attention is paid to the material structure by choosing the right materials, layer thicknesses and stack order, a robust GMR multilayer system can be made that can withstand high temperatures (>200 degrees C) and strong magnetic fields (> 200 kA/m), as has been demonstrated experimentally.