Design parameters of a 3-dimensional ultrasonic pulse controlled memory device with single domain coherently magnetized cobalt, iron and nickel particles in a non-magnetic matrix

Abstract

The coercive field Hcof single domain particles is stress sensitive. Theory shows that stress alone leads to Hc(stress) = 3λsσ/Isin a uniaxial single domain particle, if the magnetization rotates coherently. λsis the magnetostriction, σ the stress, and Isthe magnetization. It is therefore possible to orient selectively the orientation of magnetic particles in an arbitrary volume element of volume L³- at position\overrightarrow{r}in a sample, since by the proper superposition of ultrasonic pulses with pulse widthLa higher stress state can be generated at\overrightarrow{r}than in any other section of the sample. This set of pulses will reduce Hcfrom the unstressed state to H'c< Hc. An applied field H with H'c3, since this leads to an induced voltage in the coil surrounding the sample.