Metallic 10 nm Diameter Magnetic Sensors and Large-Scale Ordered Arrays

Metallic nanowires with low resistivity were grown inside insulating aluminum oxide matrices that contained very uniform columnar nanopores (10.6+/1.7 nm diameters). These nanopores can be made with large-scale order (cm²), which is desirable in applications such as hard drive read sensors and random access memories. The nanowires are grown by electrochemical deposition directly inside the alumina to avoid sidewall damage compared to nanostructures that are defined from films by lithographical patterning and etching. Specifically, trilayers of [Co(15 nm)/Cu(5 nm)/Co(10 nm)] were synthesized and measured to have 30 Ω resistance and 19% magnetoresistance. These parameters are desirable for read head sensors, especially because the nanowires described here have 1:1 aspect ratios, and 10× smaller areas and 100× lower resistances than conventional read sensors based on lithographically produced magnetic tunnel junctions. A new nanostamping technique is introduced, in which linear stamps with ordered cm² areas are imprinted onto aluminum precursors to produce ordered nanoporous aluminum oxide upon anodization. These stamps are substantially less-time consuming and cheaper to make than dot type stamps, and the order enables closely spaced arrays of CPP-GMR sensors for one-pass 2-D recording and cross recording. Importantly, the GMR sensors are grown directly into aluminum oxide with 20 nm separation. Therefore, a relatively large pattern (30 × 100 nm) can be used to produce three 10 nm-diameter GMR sensors without roughening or redeposition on sidewalls. The sensors are also already embedded in alumina for subsequent device processing.