  Typically two particles (spins) could be maximally entangled at zero
temperature, and for a certain temperature the phenomenon of entanglement
vanishes at the threshold temperature. For the Heisenberg coupled model or even
the Ising model with a transverse magnetic field, one can observe some rise of
entanglement even for a disentangled region at zero temperature. So we can
understand this emergence of entanglement at finite temperature as being due to
the mixing of some maximally entangled states with some other untangled states.
Here, we present a simple one-dimensional Ising model with alternating Ising
and Heisenberg spins in an arbitrarily oriented magnetic field, which can be
mapped onto the classical Ising model with a magnetic field. This model does
not show any evidence of entanglement at zero temperature, but surprisingly at
finite temperature rise a pairwise thermal entanglement between two untangled
spins at zero temperature, when an arbitrarily oriented magnetic field is
applied. This effect is a purely magnetic field,and the temperature dependence,
as soon as the temperature increases, causes a small increase in concurrence
achieving its maximum at around 0.1. Even for long-range entanglement, a weak
concurrence still survives. There are also some real materials that could serve
as candidates that would exhibit this effect, such as
Dy(NO$_{3}$)(DMSO)$_{2}$Cu(opba)(DMSO)$_{2}$.
