Thin film magnetic head and magnetic disk device

A thin film magnetic head comprising:

• a magneto-resistive (MR) effect element comprising:
• an MR effect film formed by sequentially layering a magnetic pinned layer, a nonmagnetic layer and a free layer;
• and
• bias magnetic field application layers formed at junction tapered parts formed on both end parts of the MR effect film in a width direction via insulating layers and foundation layers;
• wherein
• the free layer is configured to change magnetization directions in accordance with an external magnetic field,
• a magnetization direction of the magnetic pinned layer is pinned,
• the bias magnetic field application layers are configured to apply a vertical bias magnetic field to the free layer,
• the foundation layers are disposed between the insulating layers and the bias magnetic field application layers, and are configured of Cr or Cr alloy,
• the insulating layers have a two-layer structure of a lower insulating layer and a upper insulating layer sequentially viewed from the junction tapered part side,
• the lower insulating layers are configured of at least one type selected from the group consisting of Al2O3, AlN and MgO,
• the upper insulating layers are configured of a Si oxide such that the Si content of the Si oxide is in the range of 30˜56 at % (atom %) and that the atom ratio of oxygen to Si (O/Si) is in the range of 0.8˜1.3, and
• thicknesses of the lower insulating layers and the upper insulating layers are each not less than 1.5 nm.