|
| |
FIZIKA A 8 (1999) 4 , 253-260
 
THERMAL RELAXATION AND QUANTUM TUNNELLING OF THE MAGNETIZATION IN Mn12-ACETATE
DAMIR PAJIĆa, KREŠO ZADROa, TOMISLAV FRIŠČIĆb,
NENAD JUDAŠb and ERNEST MEŠTROVIĆb
aDepartment of Physics, Faculty of Science, University of
Zagreb, Bijeni cka c. 32, HR-10000 Zagreb, Croatia
bDepartment of Chemistry, Laboratory of General and Inorganic
Chemistry, Faculty of Science, University of Zagreb, Ul. kralja Zvonimira 8, HR-10000
Zagreb, Croatia
Dedicated to Professor Boran Leontić on the occasion of his 70th
birthday
Received 12 November 1999; revised manuscript received 14 February 2000
Accepted 3 March 2000
The dependence of the magnetic moment m on the temperature T and the magnetic field H
in a synthesized molecular magnet Mn12-acetate has been measured using a SQUID
magnetometer. The splitting of zero-field cooled (ZFC) and field-cooled (FC) m(T) curves
below the so-called blocking temperature TB ( » 3.6
K at H = 0) was observed. By measuring the time relaxation of m, it was found that it
tended to the same value with the same relaxation time ( » 560
s at 3 K) for both ZFC and FC processes. This indicates spin freezing below TB
and the single molecule process in the explored temperature range (2 K <
T < 4 K). The dependence of TB on applied
H was also investigated. The decreasing of TB with increasing H can be
explained in the frame of barrier reduction in the applied field.
PACS numbers: 87.15.Rn, 87.50.-a
UDC 535.217, 539.21
Keywords: Mn12-acetate, quantum tunnelling, magnetic relaxation, magnetic
bistability, blocking temperature, anisotropy barrier, spin freezing
|
