  Geometrically frustrated structures combined with competing exchange
interactions that have different magnitudes are known ingredients for achieving
exotic properties. Herein, we studied detailed structural, magnetic, thermal
(specific heat), magneto-dielectric, and magnetic exchange bias properties of a
mixed 3d - 4d spinel oxide with composition CoFeRhO$_4$. Detailed
magnetization, heat capacity, and neutron powder diffraction studies (NPD)
highlight long-range ferrimagnetic ordering with an onset at 355 K. The
magnetic structure is established using a ferrimagnetic model (collinear-type)
that has a propagation vector k = 0, 0, 0. The magneto-dielectric effect
appears below the magnetic ordering temperature, and the exchange bias (EB)
effect is observed in field cooled (FC) conditions below 355 K. The
magneto-dielectric coupling in CoFeRhO$_4$ originates due to the frustration in
the structure, collinear ferrimagnetic ordering, and uncompensated magnetic
moments. The unidirectional anisotropy resulting from the uncompensated
magnetic moments causes the room-temperature exchange bias effect. Remarkably,
the appearance of technologically important properties (ferromagnetism,
magnetodielectric effect, and EB) at room temperature in CoFeRhO$_4$ indicates
its potential use in sensors or spintronics.
