Abstract
From an analytical description of magnetic interactions combined with finite-element modelling, design rules for a giant magnetoresistance (GMR) element can be derived. For some practical designs we arrive at the conditions tPMSP < tfMSf and tpMSP ≈ γhHF. Here tp, tf, MSP and MSf are the layer thicknesses and the saturation magnetizations of the pinned and the free layer, respectively; h is the element height, HF is the ferromagnetic interlayer coupling and γ accounts for the soft magnetic environment of the sensor. We have fabricated yoke-type GMR heads in an adapted design conforming to these rules. The GMR elements were Ta/8 nm Ni80Fe20/2.8 nm Cu/6 nm Ni80Fe20/10 nm FeMn/Ta. From finite-element calculations we find that for our heads γ ≈ 2, which together with HF = 6 Oe and h = 5 μm obeys the design rules. Measurements of these heads show that indeed the optimum bias state is obtained without using the integrated bias conductor to apply a d.c. bias current. Measurements also show that the limiting factor for the head output in this case may no longer be the head efficiency (geometry), but the maximum driving amplitude (saturation) of the GMR element. This sheds new light on the current discussion whether for application of spin-valve materials in thin-film heads, a yoke-type or a shielded-type design would be advantageous.
Published Version
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