Reduced low temperature lifetimes of Bi³⁺ luminescence in magnetically ordered host lattices

This paper is specifically concerned with the radiative lifetime of the spin and orbitally forbidden Bi^{3+ 3}P₀ →¹S₀ emission transition. In diamagnetic host lattices, the lifetime of this strongly forbidden transition is long (∼1 ms). Experimental data in the literature show a drastic lifetime shortening in lattices containing Gd³⁺ compared to the diamagnetic lattices. Here, we propose that the lifetime shortenings have their origin in an internal magnetic field, the so-called molecular field, which is created at the Bi³⁺ site by the magnetically ordered Gd³⁺ sublattice. This molecular field mixes the ³P₀ and ³P₁ states to break the selection rule forbidding the ³P₀ →¹S₀ emission transition.