The atomic magnetometer is currently one of the most-sensitive sensors and plays an important role in applications for detecting weak magnetic fields. This review reports the recent progress of total-field atomic magnetometers that are one important ramification of such magnetometers, which can reach the technical level for engineering applications. The alkali-metal magnetometers, helium magnetometers, and coherent population-trapping magnetometers are included in this review. Besides, the technology trend of atomic magnetometers was analyzed for the purpose of providing a certain reference for developing the technologies in such magnetometers and for exploring their applications.

This paper analyzes the noise sources in photoelectric detection circuits with several low-noise operational amplifiers cores. The fabricated circuits are low-noise pre-amplifiers that are used for optically pumped magnetometers. In the proposed circuits, the noise levels of equivalent output voltage are calculated, and the results are in accordance with measurements. With a cooperation of several operational amplifiers, we select LT1028 from linear technologies as the core for our detection circuit, which has an output signal-to-noise ratio of more than 2 × 10⁵ up to the frequency of 100 kHz. By analyzing the individual noise sources in the detection circuit, the dominant noise source is confirmed as the photocurrent shot noise below 200 kHz. Beyond this frequency, the voltage noise source in the operational amplifier dominates. Besides, the lamp power, the radio frequency (RF) power, the temperature variations, and their influences on the sensitivity are studied and optimized. Finally, an optically pumped magnetometer with cesium head is established, showing an intrinsic sensitivity of 85 fT/√Hz. This sensitivity is realized under a geomagnetic magnetic field strength of 53 μT.

Induction magnetometer (IM) is the transducer for measuring the magnetic field's variations, which is widely used in space research, geophysical exploration, and so on. Among all kinds of IMs, IMs of 0.1 mHz to 1 Hz with negative feedback flux and chopper stabilized amplifiers are especially popular used for the magnetotelluric method in geophysical explorations. In this paper, the equivalent input magnetic noise (EIMN) of IMs of 0.1 mHz to 1 Hz is discussed and modeled. Seven main noise sources are described, numerical evaluated, and experimental modeled separately. At last, an experimental IM is built and its EIMN is measured low to 0.1 mHz to confirm the theoretical model.

A miniature three-axis induction magnetometer (IM) for borehole logging was designed, manufactured and tested. The form of the proposed IM is a cube with 12 coils at edges, which are embedded in a ring cylinder. Thus, the 12 coils are placed along with X, Y and Z axis. Each axis consists of 4 coils that are connected in series. The length, inner and outer diameters of the ring cylinder are 40 mm, 43 mm and 64 mm, respectively. The weight of the IM is 450 g. The working frequency bandwidth is set within 1Hz-10 kHz. The equivalent induction magnetic noise (EIMN) level of the IM is measured as a value less than ${\rm{pT/\sqrt Hz\ @\ 100Hz}}$ for three axes. The features and the noise performances of the proposed IM shows a potential for the use of borehole logging.