  Definitive determination of first order character of the magnetocaloric
magnetic transition remains elusive. Here we use a microcalorimetry technique
in two modes of operation to determine the contributions to entropy change from
latent heat and heat capacity separately in an engineered set of La(Fe, Mn,
Si)13 samples. We compare the properties extracted by this method with those
determined using magnetometry and propose a model independent parameter that
would allow the degree of first order character to be defined across different
families of materials. The microcalorimetry method is sufficiently sensitive to
allow observation of an additional peak feature in the low field heat capacity
associated with the presence of Mn in these samples. The feature is of magnetic
origin but is insensitive to magnetic field, explicable in terms of
inhomogeneous occupancy of Mn within the lattice resulting in antiferromagnetic
ordered Mn clusters.
