A spin-polarized current can generate microwave oscillations in a nanomagnet, offering a way to manipulate magnetic devices without external magnetic fields. This study demonstrates a technique to directly measure microwave-frequency dynamics in individual nanomagnets driven by a DC spin-polarized current. The results show that spin transfer can produce various magnetic excitations, including small-angle elliptical precession of the free layer, which confirms theoretical predictions of coherent spin-wave excitation. The nanomagnet acts like a nanoscale motor, converting electrical energy into high-frequency magnetic rotations. The experiments involved samples with a multilayer structure, where a spin-polarized current induces torque on the free layer, causing oscillations that change the device resistance. These oscillations generate time-varying voltages in the microwave range. The frequency of these oscillations depends on the magnetic field and the current, and the results are consistent with the formula for small-angle elliptical precession of a thin-film ferromagnet. As the current increases, the nanomagnet exhibits additional dynamical regimes, including large-amplitude precession and other modes. The microwave power and frequency depend on the current and magnetic field, and the results are compared with theoretical models. The study also shows that microwave signals can be observed in both high and low magnetic fields, indicating a wide range of possible magnetic dynamics. The Landau-Lifshitz-Gilbert equation was used to model the dynamics of the nanomagnet, and the results agree with the experimental data. The simulations show that large-amplitude microwave signals correspond to large-angle precession of the free-layer moment, while smaller signals correspond to small-angle precession. The study suggests that nanomagnets driven by spin-polarized currents could serve as nanoscale microwave sources or oscillators, tunable by current and magnetic field over a wide frequency range.A spin-polarized current can generate microwave oscillations in a nanomagnet, offering a way to manipulate magnetic devices without external magnetic fields. This study demonstrates a technique to directly measure microwave-frequency dynamics in individual nanomagnets driven by a DC spin-polarized current. The results show that spin transfer can produce various magnetic excitations, including small-angle elliptical precession of the free layer, which confirms theoretical predictions of coherent spin-wave excitation. The nanomagnet acts like a nanoscale motor, converting electrical energy into high-frequency magnetic rotations. The experiments involved samples with a multilayer structure, where a spin-polarized current induces torque on the free layer, causing oscillations that change the device resistance. These oscillations generate time-varying voltages in the microwave range. The frequency of these oscillations depends on the magnetic field and the current, and the results are consistent with the formula for small-angle elliptical precession of a thin-film ferromagnet. As the current increases, the nanomagnet exhibits additional dynamical regimes, including large-amplitude precession and other modes. The microwave power and frequency depend on the current and magnetic field, and the results are compared with theoretical models. The study also shows that microwave signals can be observed in both high and low magnetic fields, indicating a wide range of possible magnetic dynamics. The Landau-Lifshitz-Gilbert equation was used to model the dynamics of the nanomagnet, and the results agree with the experimental data. The simulations show that large-amplitude microwave signals correspond to large-angle precession of the free-layer moment, while smaller signals correspond to small-angle precession. The study suggests that nanomagnets driven by spin-polarized currents could serve as nanoscale microwave sources or oscillators, tunable by current and magnetic field over a wide frequency range.