a giant magnetoresistive sensor which is improved in reproduction output and peak asymmetry of read - back waveform . it is composed of a first free ferromagnetic film , a first non - magnetic film , a composite ferromagnetic film , a second non - magnetic film , and a second free ferromagnetic film , which are laminated sequentially , but has no antiferromagnetic film to fix said composite ferromagnetic film , and said composite ferromagnetic film contains a first , second , and third ferromagnetic film , which are antiferromagnetically coupled with one another , and also contains films which separate said ferromagnetic films from one another and antiferromagnetically couple them with one another .