Direct observation of volume spin waves using quantum magnetometry

Spin waves can be used as signal carriers in electronics. Because of their low dissipation, spin waves can manipulate spin qubits with negligible heat losses compared to traditional microwave circuits. This has been recently demonstrated by coupling coherent spin waves in the magnetic insulator Yttrium Iron Garnet (YIG) to a single nitrogen vacancy center (NVs) in diamond. However, sensing using NV centers requires aligning the magnetic field to the NV axis at 54deg to the film which limits what type of spin waves can be detected at weak and strong magnetic fields. Here we demonstrate the use of diamond polished along the [111] axis, which allows magnetic field alignment perpendicular to the YIG film. This approach provides direct access to volume modes thereby extending the experimentally available parameter space .