Escape rate of the nanospin system in a magnetic field: the first-order phase transition within quantum regime
Abstract
We have investigated the escape rate of the nanospin particle with a magnetic field applied along the easy axis. The model studied here is described by the Hamiltonian
H
^
=
K
1
S
^
2
z
+
K
2
S
^
2
y
+g
μ
b
H
S
^
x
,
(
K
1
>
K
2
>0)
from which the escape rate is calculated within the semiclassical approximation. We have obtained a diagram for the orders of the phase transitions depending on the anisotropy constant and the external field. For
K
2
/
K
1
>0.85
the present model reveals, for the first time, the existence of the first-order transition within the quantum regime.