A logic gate comprising a spintronic memristor device, which has two spin-polarized magnetic electrodes for injecting andor receiving a spin-polarized current and a layer of material interposed between the two electrodes for transporting the spin-polarized current from one electrode to the other. Detection of geophysically significant subsurface anomalies potentially associated with ore bodies or hydrocarbon deposits can be made by vehicle mounted surface or airborne regional gravitational studies. The component is trimmed by applying a sequence of heat pulses the a heating element, which could be the component itself or a separate element.