Spontaneous micromagnetic oscillation in a thin-film head

Reported are experiments on a spontaneous micromagnetic oscillation found in a thin-film tape head excited by a typical write current. The effect is revealed as an additive low-frequency signal (150 to 300 KHz), written into the tape when writing with a higher frequency (e.g., 2.5 MHz). It is shown to be associated with writing by cross reading/writing with the two heads. The source is micromagnetic as demonstrated by detecting an induced EMF in the coil when exciting the head outside the tape path.