טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentShafir Oren
SubjectInvestigating the Influence of Nuclear Fluctuations on
Magnetic Quantum Tunneling
DepartmentDepartment of Physics
Supervisor Professor Keren Amit
Full Thesis textFull thesis text - English Version


Abstract

Molecular clusters of paramagnetic metal ions have been widely investigated as a model for magnetism at the nanoscale, especially for quantum effects such as the tunneling of the magnetic moment. The molecular magnet Fe8, is a representative compound in which quantum tunneling of magnetization (QTM) has been observed.


The main objective of this work is to observe the effect of the nuclear spins on the QTM in Fe8 by examining the influence of radio frequency (RF) on its hysteresis loop. RF pulse sequence can change the nuclear spin temperature without changing the electron spin temperature. In our experiment we measure the magnetization curve in the presence of RF, unfortunately we see no effect. This puts an experimental limit on theory.


As a by product of our experiment, we discovered a jump in the temperature every time there is a step in the magnetization curve. We present results which show that the origin of those jumps is not from the moving parts of the system, but from the sample.  Others measurements show that the thermometer heats up from bursts of photons from the sample, rather than phonons. We consider in the discussion the possibility of observing super-radiance.