Contents


Preface

Knowledge of magnetism spans from Ancient Greece to present day. Current theories of

magnetism bring to light new applications, new features, and new models.

Magnetism is the source of two phenomena in physics: electric current and spin magnetic moments of elementary particles. As such, much attention is paid to lowdimensional structures. As the space dimension of a physical system decreases, magnetic ordering tends to vanish as fluctuations become quite significant. As known, there is no spontaneous magnetization in systems in one dimension at any nonzero temperature; for instance, the isotropic spin-s Heisenberg model, hard-core, and any system with finite range interactions. Nevertheless, the mean-field approximation constitutes an example of the state of magnetic ordering of a chain of spins with long-range microscopic interactions giving anomalous ferromagnetism cases in one dimension. Therefore, an accurate description of magnetic ordering phases illustrates concepts about the critical

behavior and phase change and possible applications of new magnetic devices.

M. Hsini, S. Zemni, In Chapter 2 "Modeling the Magnetocaloric Effect of

in the modeling and application of magnetometers.

magnetometry and wide field-of-view optics.

materials science, metrology, astronomy, and geophysics.

Following the Introductory chapter, four chapters cover topics related to recent advances

Nd0.67Ba0.33Mn0.98Fe0.02O3 by the Mean Field Theory," M. Hsini and S. Zemni combine mean-field theory and the Bean–Rodbell model to justify the magnetocaloric effect (MCE) in a sample. They derive expressions to rating the magnetic entropy change under various magnetic fields and compare theoretical to experimental curves.

H. López Loera, In Chapter 3 "The Magnetometry—A Primary Tool in the Prospection of Underground Water," H. López Loera presents a geophysical methodology that shows the potential of combining natural and induced methods to locate confined aquifers in zones with a high probability of locating groundwater in the Mexican Mesa Central.

In Chapter 4 "Atomic Scale Magnetic Sensing and Imaging Based on Diamond NV Centers," M. Lee, J. Yoon, and D. Lee review the basic sensing mechanisms of the nitrogen-vacancy (NV) center and introduce imaging applications based on scanning

Finally, in Chapter 5 "SQUID Magnetometers, Josephson Junctions, Confinement and BCS Theory of Superconductivity," N. Khaneja discusses some theoretical aspects of a SQUID magnetometer, as its sensitivity makes it possible to apply to biomagnetism,

**Sergio Curilef**

Antofagasta, Chile

Universidad Católica del Norte,
