Point contacts between high anisotropy ferromagnetic SmCo _5 and normal metal Cu are used to achieve a strong spin-population inversion in the contact core. Subjected to microwave irradiation in resonance with the Zeeman splitting in Cu. the inverted spin population relaxes through stimulated spin-flip photon emission. detected as peaks in the point-contact resistance. https://vacuumdoctores.shop/product-category/industrial-vacuum-accessory/