High Magnetostriction of magnetic garnet

 We are developing the Magneto-Optic Spatial Light Modulator (MOSLM) for hologram volumetric recording. A switching speed of MOSLM is faster than conventional SLM, therefore MOSLM is promising device for hologram volumetric recording. There is the Current driven MOSLM (i-MOSLM) and Voltage driven MOSLM (v-MOSLM). I-MOSLM is already fabricated. We are now developing the v-MOSLM. At the low driving power and electric heating, v-MOSLM has advantage form i-MOSLM. In the light modulation, when an incident light goes through across the magnetic garnet, the polarization direction of the light was changed depending on the Faraday effect. In other words, MOSLM is changing the polarization direction by the modulating of magnetization vector. Commonly, external magnetic field is used to modulating the magnetization (i-MOSLM). But our v-MOSLM employs an inverse magnetostericton for modulating the magnetization. The process of the switching of light with v-MOSLM is shown below.
Fig. 1 The illustration of v-MOSLM. The metal as a reflection layer and electrode at interface between magnetic garnet and piezoelectric film is shown.
  • 1) Voltage is applied to piezoelectric layer.
  • 2) Stress is induced around piezoelectric layer.
  • 3) Magnetic garnet film is given the stress.
  • 4) The magnetization of magnetic garnet film is changed by inverse magnetosteriction.
  • 5) The light which through across the magnetic garnet film is modulated.
An efficient of the light modulating is related the saturation magnetostericton of magnetic garnet film. Therefore, we are studying on enlarge the saturation magentostriction of magnetic garnet film. So far, by adding the Dysprosium to Bismuth substituted Yttrium Iron garnet (Bi:YIG), we enhance the saturation magnetostriction to 3 times higher than Bi:YIG.
Fig. 2 The magnetostricton of Dysprosium added Bi:YIG
Magnetostriction is a property of ferromagnetic materials that causes them to change their shape when subjected to a magnetic field. Oppositely, magnetization can be changed by deform there shape. It is called as inverse magnetosteriction or Villari effect.