Dear Colleagues,

The AC magnetic susceptibility (ACMS) technique is a powerful tool which makes it possible to investigate the magnetic response of a material when an AC magnetic field is applied. By changing the AC field amplitude and frequency, it is possible to probe the different magnetic behaviors and obtain information about the characteristic magnetic properties of the material. In particular, the study of superconductors by means of the ACMS technique enables researchers to determine the shielding and dissipation properties of the investigated sample by analyzing the real and imaginary part of the AC fundamental harmonic, respectively, together with other important features for applications such as critical temperature, critical current density in the AC regime, pinning properties, etc. Moreover, by analyzing the first- and third-harmonic components it is possible to study the vortex dynamics of the sample, distinguishing different dissipative regimes. Concerning magnetic materials, the ACMS technique makes it possible to study the different magnetic phase transitions of the investigated sample together with the relaxation phenomena which are correlated to the spin dynamics that very often are not recognizable with DC magnetic measurements. The features that can be studied include: the freezing temperature of the spin glass systems, which can be probed using the ACMS technique since this temperature is sensible to the AC frequency variations; the blocking temperature of magnetic nanoparticles, which can be determined by the imaginary component of the fundamental harmonic; the Curie temperature for ferromagnetic samples, which can be examined by varying the AC magnetic field amplitude and frequency, also individuating various models of magnetic interactions.

This Special Issue will be focused on the AC magnetic susceptibility technique applied to superconducting (low-temperature, high-temperature, iron-based, etc.) and magnetic (spin glass, ferro/antiferro/ferri-magnetic materials, magnetic nanoparticles, etc.) materials and will include, but not be limited to, the following topics:

• Fundamental and third harmonic of AC magnetic susceptibility in superconducting materials;
• Vortex dynamics and dissipative regimes in superconductors in AC magnetic field;
• AC losses in Type-II superconductors;
• AC amplitude and frequency dependencies of the properties of ferromagnetic and antiferromagnetic materials;
• Magnetic phase transitions;
• Spin glass relaxation properties;
• Magnetic nanoparticles;
• Blocking temperature and superparamagnetic behavior.

It is our pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Prof. Massimiliano Polichetti
Dr. Armando Galluzzi
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• AC magnetic characterization of superconducting and magnetic materials
• multi-harmonic AC susceptibility
• vortex dynamics and pinning properties in AC field
• magnetic phase transitions