An increase in external temperature or internal heating by writing can induce protrusion or strain of thin film layers in a magnetic recording head. To profile the protrusion, the surface topography and the temperature distribution are imaged in fixed heads by scanning probe and optical microscopy. Near the poles and the shields, the protrusion is at a peak, producing a risk of head-disk interaction. The dynamics are elucidated in flying heads over a disk by measuring the amplitude of a reference pattern with the read head. The temporal profiling technique can be applied both in component testing on spinstands and reliability testing in fully integrated disk drives. For either heating or cooling of the heads, the characteristic time constant for protrusion is 100 s and reaches 95% of the plateau after 1 ms. The protrusion is linear with temperature and is reversible, implying that the strains are within the elastic limit. Furthermore, variation of the write pulse shape suggests that Joule heating is more significant than eddy current or hysteresis losses in inducing protrusion.Index Terms-Magnetic heads, magnetic recording mechanical factors, strain, thermal protrusion.

Perpendicular recording technology has become the main stream for 130 Gb/in 2 HDD products. In this paper, challenges in perpendicular write head are discussed. Design tradeoffs and concerns of narrow-track single-pole heads, trailing shield heads, floating TS heads, and wrapped-around-shield (WAS) heads are discussed. Experimental data show that WAS heads provide good narrow track and high linear density performance. An areal density of 343 Gb/in 2 has been achieved at a very aggressive magnetic spacing condition.

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