“Magnetometers”, “Superconductive” electromagnetic sensors, and specially designed components therefor, as follows a. “Magnetometers”, having a ‘sensitivity’ lower (better) than 1.0 nT (rms) per square root Hz. . b. “Superconductive” electromagnetic sensors and components manufactured from “superconductive” materials, having all of the following: b.1. Designed for operation at temperatures below the “critical temperature” of at least one of their “superconductive” constituents (including Josephson effect devices or “superconductive” quantum interference devices (SQUIDS)); b.2. Designed for sensing electromagnetic field variations at frequencies of 1 KHz or less; and b.3. Having any of the following: b.3.a. Incorporating thin‑film SQUIDS with a minimum feature size of less than 2 μm and with associated input and output coupling circuits; b.3.b. Designed to operate with a magnetic field slew rate exceeding 1 x 10 magnetic flux quanta per second; 6 b.3.c. Designed to function without magnetic shielding in the earth’s ambient magnetic field; or b.3.d. Having a temperature coefficient less (smaller) than 0.1 magnetic flux quantum/K.