Reliability of Magnetoresistive Bubble Sensors

Head reliability of AMR sensors based on thermal stress tests

“…The 1.25 Ϯ 0.15 eV activation energy measured for stripe oxidation at the ABS matches the value of 1.2 Ϯ 0.4 eV measured on Permalloy sheets exposed to air [9]. The 1.25 Ϯ 0.15 eV activation energy measured for stripe oxidation at the ABS matches the value of 1.2 Ϯ 0.4 eV measured on Permalloy sheets exposed to air [9].…”

“…The measured activation energy of 2.1 Ϯ 0.1 eV for the large resistance increases and the amplitude degradation for the sensors with t mr values of 30.0 and 40.0 nm match the value of 2.0 Ϯ 0.1 eV measured on 20.0-nm-thick dual-stripe AMR sensors [6] and the 2.2 Ϯ 0.5 eV for magnetic changes on 21.0-nm-thick Permalloy stripes [9]. Furthermore, the increase in the rate prefactor measured in this study (to 6.3 ϫ 10 Ϫ16 hr Ϫ1 from 6.3 ϫ 10 Ϫ15 hr Ϫ1 for the sensors with a t mr of 30.0 nm compared with the sensors with a t mr of 40.0 nm) correlates with a rate prefactor of 10 Ϫ16 hr Ϫ1 measured by Zolla [6] for a 20.0-nm-thick stripe.…”

“…While published papers have addressed reliability associated with large resistance changes or drops in amplitude [5][6][7][8][9], few, if any, have directly addressed changes in signal distortion or magnetic-transition densitydependent responses (Wallace spacing losses) [10]. Signal distortion arises from a nonlinear response to magnetic field magnitude or direction.…”

Hand-held Magnetoresistive Transducer

“…This current density level corresponds to a current I of 40 to 100 mA through the cross sections given in Table I, which is far in excess of values that would cause excessive heating without elaborate heat sinking. In the device configuration described below, temperature rises of 25°C above ambient can be achieved with a current I = 10 mAo This temperature rise and current level are well within the safe limits established in [7] and give output signals greater than 10mV, a level consistent with inexpensive semiconductor amplifiers. It is Link spring keeper and dimensions were chosen to achieve a negligible lead resistance.…”

“…The only other potentially large source of noise in an MR sensor is the modulation of resistance due to mechanical shock or 545 thermal transients. For example, the temperature coefficient of resistivity of NiFe films is typically 0.3%;CC and may be as high as 0.5%;CC [7]. Because the relative signall1R max l R~2 to 4%, thermal transients ofless than 10°C can give rise to a noise as large as the magnetic signal.…”