Fig. 2: The Hahn-echo decay of Cr³⁺ and Fe³⁺ spin centers in HDPs host.

A An illustration of the Hahn-echo electron spin resonance experiment, with a pulse sequence of \(\pi /2\to \tau \to \pi \to \tau \to {echo}\). B A magnetic field-sweep Hahn-echo experiment of the Cr³⁺ centers in the Cs₂NaInCl₆ (Cr[Na]) samples performed at 4 K. The echo signal decays with time evolution \(2\tau\). The central resonant field is 350.2 mT, corresponding to the Cr³⁺ ions with \(g\)= 1.981. C A comparison of echo decay and spin decoherence time (\({T}_{2}\)) obtained for two different TM centers (Cr³⁺ and Fe³⁺) in Cs₂NaInCl₆ host at 4 K and 20 K. Echo decay curves were fitted with a two-exponential model at 4 K and a single-exponential model at 20 K. The individual components of the 4 K fit are shown by the gray-dotted lines for the fast decay term and the gray-dashed lines for the slow decay term. The overall fitting curves for both temperatures are represented by the solid black lines.