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.
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