Demonstrating a tunneling magneto-resistive read head

We demonstrate the feasibility of a read head using a high-resistance spin-dependent tunneling (SDT) junction. The head consists of a 1.5 μm or 1.7 μm wide flux guide on top of the junction. The junction is about 0.8 μm wide and varies in height, There is a pinned layer at the bottom of the stack. The tunnel barrier is made by plasma oxidation of about 10 Å of aluminum. The barrier has resistance of about 3.7 kΩ μm², leading to a typical head resistance of a few kΩ. The heads are lapped to the edge of the junction, and show 5% to 8% TMR during transfer curve measurement. Isolated pulses during the spin stand test shows large signal up to 5.7 mV. We find a voltage sensing preamp is a better choice over a current sensing one