Patent ID: 7522392

Claim:
A magnetoresistive sensor capable of sensing an external magnetic field and having a sensing end for exposure to the external magnetic field and a back end spaced from the sensing end, the sensor being a magnetoresistive read head for reading magnetically recorded data from a magnetic recording medium and comprising: an electrically conductive substrate, the substrate being a first shield S 1 formed of magnetically permeable material; a first electrical insulator on S 1 , said first electrical insulator being a first gap layer G 1 ; an electrically conductive strip on the insulator and having a first end at the sensing end of the sensor and a second end at the back end of the sensor; a first tunnel barrier on the strip at the first end; a sensing ferromagnetic layer on the first tunnel barrier and having an in-plane magnetization direction oriented substantially in a first direction in the absence of an external magnetic field, said sensing layer magnetization direction being substantially free to rotate in the presence of an external magnetic field; an electrically conductive layer on the sensing layer, said electrically conductive layer being a second shield S 2 formed of magnetically permeable material, the spacing between S 1 and S 2 at the sensing end of the sensor defining a read gap and wherein there is no second gap layer G 2 in said read gap; a second tunnel barrier on the strip at the second end; a fixed ferromagnetic layer on the second tunnel barrier and having an in-plane magnetization direction oriented in a second direction substantially orthogonal to said first direction and substantially prevented from rotation in the presence of an applied magnetic field in the range of interest; and an electrical terminal on the fixed layer, the terminal being electrically insulated from the electrically conductive layer on the sensing layer; whereby when current is directed through the terminal, the fixed layer and the second tunnel barrier into the second end of the strip at the back end of the sensor, the detection of a change in electrical resistance between the electrically conductive layer on the sensing layer and the electrically conductive substrate will indicate the presence of an external magnetic field at the sensing end of the sensor.