  We report the detection of paramagnetic resonance in the double perovskite
La2NiMnO6 at room temperature for microwave magnetic fields with frequencies, f
= 1 GHz to 5 GHz, using two cavity-less methods. We use an indirect impedance
method which makes use of a radio frequency impedance analyzer and a folded
copper strip coil for the frequency range f = 1 to 2.2 GHz. In this method,
when an applied dc magnetic field is swept, high-frequency resistance of the
strip coil exhibits a sharp peak and the reactance curve crosses zero
exhibiting resonance. A lock-in based broadband setup using a coplanar
waveguide for microwave excitation was used for f = 2 to 5 GHz The resonance
fields (Hr) obtained from both the techniques increase linearly with frequency
and a large spectroscopic g-factor, equal to 2.1284, which supports the
presence of Ni2+ cation with strong spin-orbit coupling. Line shape analysis
and analytical fitting were performed to characterize the material in terms of
its initial susceptibility and damping parameters.
