We have detected the zero-field electron-spin resonance signal of Al2O3 with ∼1000 ppm Cr3+ using an edge Josephson junction. The sample comprises the substrate upon which the junction was fabricated and the coupling to the electron-spin resonance is via the solitons which exist in these "long" devices.
Mehran, F.; Barnes, S. E.; Chi, C. C.; Sandstrom, R. L.; and Umbach, C. P., "Observation Of Al2O3: Cr3+ Magnetic Resonance Via Solitons In Long Josephson Junctions" (1987). Physics Articles and Papers. 68.