CryoBIND now offers a room temperature, high frequency ac susceptibility systems, BROWNEEL®. Unlike CryoBIND cryogenic systems, with their coils designed to cover the frequency range up to 5 kHz, the coils of the BROWNEEL® systems enables measurement of the frequency dependent susceptibility up to 250.000 Hz. The BROWNEEL® models are dedicated primarily to research of magnetic dynamics in systems of magnetic nanoparticles & ferrofluids, revealing different types of magnetic relaxation phenomena (Neel, Brown ...).

System characteristics:


Measuring ac field:

• -small field system: Hac up to 2.5 Oe.
• -high field system (currently under development): Hac at the order of 100 Oe.
  
  
• In both variants the field strength is kept constant at all frequencies within the measuring frequency range.

Frequency range: 10 Hz - 250.000 Hz.

Sample container: Glass or plastic ampoule, 6mm external dia.

Sample positioning: Software-controlled stepper motor positioner.

• Frequency dependent ac susceptibility of a reference Cu sample. In nonmagnetic Cu frequency dependence relies on eddy currents induced by the applied field. The screening effect of eddy currents increases with increasing frequency. Thus the effective sample diamagnetism grows with the frequency (i.e., χ’ becomes more negative) while the dissipation, represented by χ’‘, passes through a maximum.