  The purpose of this paper is to study the thermodynamic equilibrium
properties of a collection of non-interacting three-dimensional (3D)
magnetically anisotropic nanoparticles in the light of classical statistical
physics. Pertaining to the angular dependence ($\alpha$) of the magnetic field
with the anisotropy axis, energy landscape plots are obtained which reveal a
continuous transition from a double well to a single well for
$\alpha=\frac{\pi}{2}$ and show asymmetric bistable shape for other values of
$\alpha$. The present analysis is related with the interpretation of
equilibrium magnetization and static susceptibility of nanomagnetic system as a
function of external magnetic field, $B$, and temperature, $T$. The
magnetization and susceptibility confirms the non Langevin behaviour of
magneto-anisotropic monodomain particles. The susceptibility analysis
establishes the ferromagnetic, antiferromagnetic and paramagnetic like coupling
for various $\alpha$. This study reveals the essential role of magneto
anisotropic energy in the interpretation of the magnetic behaviour of a
collection of noninteracting single domain nanoparticles.
