The performance of state-of-the-art tunneling magnetoresistive (TMR) heads depends on the thickness of insulating layers less than a few nanometers thick that separate two magnetic films. We have used low energy electron nanoscale-luminescence (LEEN) spectroscopy to observe optical emission from TMR test structures with buried insulating oxides less than a few nanometers thick. TMR structures grown by metal evaporation consisted of a 0.8-3 nm Al oxide layer on a 2.4 nm CoFe alloy (84: 16) on a multilayer metal-on-Si substrate, all capped with a 0.4 nm CoFe with Pt overlayer. LEEN studies with excitation energies ranging from 0.5 to 3 keV enabled emissions from the buried oxide layers versus the free surface to be distinguished. We used different compositions, thicknesses, and oxidation exposures to separate At oxide from transition metal oxide emissions, as well as from the ambient-exposed Pt surface. A broad peak centered at 2.2-2.5 eV increased with O plasma exposure to At films on the CoFe alloy. Emission from oxidized CoFe without At consists of a broad emission centered at 2.5 eV. Common to all these spectra is emission at 1.8 eV, which energy-dependent LEEN demonstrates is due to the ambient-exposed Pt. Spectral changes versus oxygen exposure reveal the regime separating oxidation of the magnetic and nonmagnetic layers.