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We investigated the effect of specular reflection on the anisotropic magnetoresistance (AMR) of magnetic thin films. The sheet conductance is calculated as a function of the angle between magnetization and current from the microscopic transport parameters by using an extension of the Fuchs–Sondheimer theory. The calculation combines specular reflection on the film interfaces with mean-free paths which depend on the angle between the local magnetization and the electron velocity. The theoretical results are compared with experimental ones. Specular reflection can explain the quite large AMR amplitude observed in thin NiFe films used in the last generation of AMR heads.

We have demonstrated a robust magnetic tunnel junction (MTJ) with a resistance-area product RA=8 Ω−µm 2 that simultaneously satisfies the statistical requirements of high tunneling magnetoresistance TMR > 15σ(R p ), write threshold spread σ(Vw)/ <7.1%, breakdown-to-write voltage margin over 0.5V, readinduced disturbance rate below 10 -9 , and sufficient write endurance, and is free of unwanted write-induced magnetic reversal. The statistics suggest that a 64Mb chip at the 90-nm node is feasible. IntroductionThe density of STT-RAM [1] can be as competitive with that of embedded DRAM. It is more scalable and consumes less power than the conventional field-MRAM [2]. This paper describes an STT-MRAM with 70x210 nm 2 MTJ devices. This MTJ provides sufficient statistical margins among read-and writeoperation and satisfies the junction long-term reliability requirements.

Giant magneto-resistance estimated from direct observation of nanoscale ferromagnetic domain evolution in La0.325Pr0.3Ca0.375MnO3 J. Appl. Phys. 112, 053924 (2012) Electrical determination of relative chirality direction in a Co/Cu/Co ferromagnetic ring Appl. Phys. Lett. 101, 062409 (2012) Temperature and frequency dependent giant magnetodielectric coupling in DyMn0.33Fe0.67O3 J. Appl. Phys. 112, 013920 (2012) Magnetoresistive effects in perpendicularly magnetized Tb-Co alloy based thin films and spin valvesWe present an analytical calculation of the shape of the magnetoresistive response of spin-valve structures with synthetic antiferromagnetic pinned layer, i.e., of the form buffer/ferromagnet1/Cu/ ferromagnet2/Ru/ferromagnet3/antiferromagnet. The magnetization reversal in the three magnetic layers is assumed to occur via coherent rotation. An analytical expression of the whole hysteresis loop is given as a function of the characteristic parameters of the system ͑coupling strength through the Ru spacer, ferromagnet3/antiferromagnet pinning energy͒. We also extended a code based on the Boltzmann equation of transport to calculate the giant magnetoresistance ͑GMR͒ amplitude in these structures from the microscopic transport parameters. In order to explain the relatively high GMR amplitude experimentally observed in such spin valves, it is shown that some degree of specular reflection must be introduced at the ferromagnet2/Ru interface. Good agreement with both the shape and amplitude of the experimental magnetoresistance curves can be obtained.

The breakdown distribution of a magnetic tunnel junction (MTJ) with an ultrathin (∼1.2 nm) MgO barrier was studied, and two distinct distributions were identified. The breakdown distribution with high value demonstrates a wide peak-to-peak separation (∼13.4σ) to the critical spin torque induced switching voltage. However, the peak-to-peak separation is only ∼8.4σ for the devices showing low breakdown value. Both abrupt and gradual breakdown events were observed in two distributions. The dependence of the percentage of low breakdown devices as a function of bias polarity, test and stress conditions, MTJ film properties, and process conditions was investigated. The low breakdown percentage can be significantly reduced by increasing the RA value and MTJ process optimization.