A new band in Cr 3+ ‐doped MgAl 2 O 4 natural spinel at room temperature

Time resolved photoluminescence spectra of natural MgAl 2 O 4 spinel doped with Cr 3+ ions have been investigated at room temperature in the wavelength range between 380 and 800 nm. Using several excitation sources from the different lasers we have observed a new band, namely K, with a peak of 15,547 cm −1 (643.2 nm) and the transition process of photoluminescent lines among the electronic levels of the Cr 3+ ion. In terms of the experimental results and the Tanabe‐Sugano diagram, we strongly propose that the K‐band originates from the electric dipole transition, 2 E g → 4 A 2g in the strong crystal field with Dq / B > 2.3. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)