Optically Induced Magnetization in Ruby

The magnetization of ruby in a magnetic field at 300^∘{}K is changed when the ruby is optically pumped with linearly polarized radiation from a Q-switched ruby laser. With a magnetic field parallel to the trigonal axis, laser light polarized parallel to this axis induces transitions from the spin ±{}{} levels of the ⁴A₂ ground state to the levels of the Ē(²E) excited state. The change in Mz is linearly proportional to H except near the anticrossing points of the ⁴A₂ spin levels at 2.07 and 4.14 kG. At these field strengths, there is an enhancement of the magnetization caused by state mixing of the ⁴A₂ wave functions. When H has a small component perpendicular to the z axis, a magnetization is detected parallel to this component in the vicinity of 4.14 kG. The effect requires a long ground-state relaxation time. In a separate experiment, the relaxation of Mz was found to vary from 0.13 {μ}sec in zero magnetic field to a constant value of 0.57 {μ}sec for fields above 60 G.