High Resistivity, High Permeability Shield Spacers for Magnetoresistive Head
Original Publication Date: 2000-Dec-01
Included in the Prior Art Database: 2003-Jun-19
Described is a magnetic recording head read structure which maintains high linear resolution of the readback signal from a written track, but reduces the tendency to shield shorts, that attends the use of narrow read gaps at high linear density. This is accomplished by the incorporation of high resistivity, high permeability shield spacers into the read gap/shield structure of the magnetic recording head. A novel feature of the invention is the use of materials possessing this unique combination of high resistivity with high permeability properties. As areal recording densities rise, linear densities within the recorded track increase. This increase of linear density imposes constraints on the read gap thickness which must decrease inversely with the increase in linear density. Unfortunately, reducing the gap dimension is becoming increasingly less compatible with the demands of high device reliability and high yields that are required for a viable production program. It is an all too true fact that the processes and materials relied upon to bring these scaled designs to fruition have their own sets of scaling laws which are often overlooked and taken for granted in the drive to smaller dimensions. In particular, when the upper and lower gap insulator dimensions of the read structure push down to dimensions on the order of tens of nanometers, the usual materials, and structures used result in ever increasing incidences of shorts between the sensor itself and the shields used to define the read gap dimension. Thus, the dimension of the insulating read gap is caught on the horns of a dilemma between reducing the dimension to improve linear density and increasing the dimension to improve yields. The essence of this invention is to separate these two design constraints by the combination of a novel material with a new read gap/shield structure. This is accomplished by incorporating shield spacers with a suitable thickness into the gap structure, shield spacers which have material properties useful both as shields and as gaps. In effect, these electrically insulating, magnetically active shield spacers provide supplementary thickness to that of the conventional, non-magnetic, insulating gaps, that are defined by the linear resolution of the written track, to stand off conductive shields from the sensor, and buffer the sensor from the occurrence of shield shorts. The key to implementing this invention is the choice of a material for the shield spacer with high resistivity to prevent shield shorts, and high permeability to act as a good shield extension in defining the read gap dimension. Thus, the material's properties allow for the separation of the read gap dimension from the shield short spacing dimension. In addition, this invention provides a further advantage in that the thicknesses of the non-magnetic, insulating gaps are scaleable to arbitrarily vanishingly small dimensions which will become important as linear densities approach the thickness dimension of the sensor itself. A preferred embodiment of the invention comprises a magnetic recording head read structure having: a high conductivity, high permeability, lower shield, preferably made of a material selected from the group consisting of permalloy, and sendust; a high resistivity, high permeability, lower shield spacer, preferably made of FeHfON, disposed on top of the lower shield, with a thickness sufficient to prevent shield shorts between the lower shield and a magnetoresistive read sensor; an electrically insulating, lower read gap, preferably made of Al 2 O 3 , disposed on top of the lower shield spacer, with a thickness determined by the required linear recording density; a magnetoresistive sensor, preferably a spin valve, disposed on top of the lower insulating gap; a second, electrically insulating, upper read gap, preferably made of Al 2 O 3 , disposed on top of the sensor, with a thickness set by the required linear recording density; a second, high resistivity, high permeability, upper shield spacer, preferably made of FeHfON, disposed on top of the electrically insulating, upper read gap, with a thickness sufficient to prevent shield shorts between an upper shield and the magnetoresistive read sensor; and, a high conductivity, high permeability, upper shield, preferably made of permalloy.