β-Detected NMR Search for Magnetic Phase Separation in Epitaxial GaAs:Mn

To test for the microscopic magnetic phase separation in the dilute magnetic semiconductor Ga1−xMnxAs sug-gested by low energy muon spin rotation measurements[1], , we present a detailed analysis of the amplitudes of the 8Li β-detected nuclear magnetic resonance in an epitaxially grown thin film of x = 5.4% Mn doped GaAs on a semi-insulating GaAs substrate with magnetic transition temperature TC =72 K. The spectrum at 100 K corresponds to 73% of the full room temperature amplitude, and at 60 K to about 62%. The 11% loss of signal through the magnetic tran-sition is much smaller than that ∼ 50% found by low energy μSR[1], , and may be entirely due to an amplitude change intrinsic to GaAs. This lack of evidence for phase separation is, however, consistent with the full volume fraction magnetism found by a second low energy μSR measurement on a different sample using weak transverse field[2].