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Both the heat generated by the current in the write coil and the rise in the surrounding temperature cause local thermal protrusion (TPR) on magnetic-head elements. Such protrusion reduces the flying height of the head slider below the design value, thus reducing the safety margin for head-disk interference. To analyze this problem, we numerically simulated the heat transfer in the head slider, the thermal deformation of the head, and the flying-height change of the slider resulting from the deformation. The parameter study shows that decreasing the thickness of the alumina base coat or increasing the size of the pole and shields can reduce the magnitude of write-current-induced thermal protrusion (W-TPR). On the other hand, a longer pole and shields increase ambient-temperature-induced protrusion (T-TPR). For W-TPR, the reduced flying height is partly compensated by increased air pressure on the air-bearing surface (ABS). However, almost the entire magnitude of T-PTR translates into flying-height reduction.