Figure 2.

Example of temperature response as a function of time and concentration of the MNPs (maghemite-magnetite mixture) under AMF. The temperature was measured with the Ambrell EasyHeat system (Magnetic Field Amplitude H0 = 30.1 kA/m, Frequency f = 275.0 kHz) using a Yokogawa fiber-optic system with Tpmeter3 software. The optical fiber was immersed in the magnetic fluid, so that the tip of the fiber would coincide with the central point of the magnetic fluid volume. A time interval of ~5 min was allowed before switching on the magnetic field, so that the system would reach the thermal equilibrium state. The desirable magnetic field could be achieved by adjusting the coil current via the EasyHeat system. A time step of 30 s was selected between consecutive temperature recordings and the total heating process lasted 1500 s. Subsequently, the field was switched off, but the data acquisition process was continued, in order to obtain the cooling phase of the fluid. (Unpublished data).