Contribution of hysteresis loss to the hyperthermal effect in the cobalt magnetic fluid

A. Skumiel¹ - A. Józefczak¹ - A. Szlaferek² - W. Kowalski² - M. Timko^3} - P. Kopċanský³ - M. Koneracká³

¹ Institute of Acoustics, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
² Institute of Molecular Physics, PAS, Smoluchowskiego 17, 60-179 Poznań, Poland
³ Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, Košice, Slovakia

Abstract
The paper reports results of hyperthermia experiments performed with a magnetic fluid containing CoFe₂O₄ particles subjected to a magnetic field of a few intensities (0 < H_AC ≤ 2350 Am⁻¹) and at the frequency f = 736 kHz. To determine the structure of the fluid and its magnetic properties, the magnetic measurements were made by a vibrating sample magnetometer (VSM) in a field, whose intensity was changed in a wide range (H = ±800 kAm⁻¹). An additional study by the AFM method permitted estimation of the mean hydrodynamic volume of nanoparticles and the mean Brownian relaxation time of magnetisation. In the experimental conditions, the majority of the magnetic particles underwent demagnetization of the Brownian type . In order to determine the percent contribution of the hysteresis loss P_h to the total energy loss P_total, a few hysteresis loops (VSM) have been determined for the magnetic field amplitudes typical of medical applications H_AC < 30 kAm⁻¹. Tables 2, Figs 8, Refs 13.