  We compute the heat generated by (non-interacting) nanomagnets subjected to
an alternating magnetic field (AMF) and study its transfer to the hosting
medium and environment. For the first task, we compute the heat generated by
the nanomagnets (or the specific absorption rate) using the ac susceptibility
in the linear regime. For the second task, the loss of heat to the environment
is modeled with the help of a balance (macroscopic) equation based on Newton's
law of cooling. This equation is solved both numerically and analytically for a
generic ferrofluid and the analytical solution renders a very good
approximation to the general balance equation. Then, we investigate the effects
of AMF frequency and amplitude on the temperature elevation during its temporal
evolution. Finally, using the available experimental data for maghemite and
magnetite ferrofluids, we discuss the behavior of Newton's heat transfer
coefficient in terms of the AMF amplitude and frequency. These results could
trigger experimental investigations of this coefficient which characterizes the
rate of heating in a ferrofluid, with the aim to build more refined models for
the mechanisms of heat generation and its diffusion in ferrofluids used in
magnetic hyperthermia.
