  We report complex magnetic, magnetoresistance (MR) and magnetocaloric
properties of Gd4RhAl and Tb4RhAl forming in the Gd4RhIn type cubic structure.
Though the synthesis of the compounds was reported long ago, to our knowledge,
no attempt was made to investigate the properties of these compounds. The
present results of ac and dc magnetization, electrical resistivity and
heat-capacity measurements down to 1.8 K establish that these compounds undergo
antiferromagnetic order initially, followed by complex spin-glass features with
decreasing temperature. These characteristic temperatures are: For Gd case, TN
is about 46K and TG is about 21 K, and for Tb, about 32 and 28 K respectively.
Additionally, there are field induced magnetic effects, interestingly leading
to non-monotonic variations in MR. There is a significant MR over a wide
temperature range above TN, similar to the behavior of magnetocaloric effect
(MCE) as measured by isothermal entropy change (DeltaS). An intriguing finding
we made is that DeltaS at the onset of magnetic order is significantly larger
for the Tb compound than that observed for the Gd analogue near its TN. On the
basis of this observation in a cubic material, we raise a question whether
aspherical nature of the 4f orbital can play a role to enhance MCE under
favorable circumstances, a clue that could be useful to find materials for
magnetocaloric applications.
