  We report on a voltage tunable radio-frequency (RF) detector based on a
magnetic tunnel junction (MTJ). The spin-torque diode effect is used to excite
and/or detect RF oscillations in the magnetic free layer of the MTJ. In order
to reduce the overall in-plane magnetic anisotropy of the free layer, we take
advantage of the perpendicular magnetic anisotropy at the interface between
ferromagnetic and insulating layers. The applied bias voltage is shown to have
a significant influence on the magnetic anisotropy, and thus on the resonance
frequency of the device. This influence also depends on the voltage polarity.
The obtained results are accounted for in terms of the interplay of
spin-transfer-torque and voltage-controlled magnetic anisotropy effects.
