Experimental evidences of singlet to triplet transition in a spin cluster compound

• Magnetic field induced energy level crossing is reported for NH4CuPO4·H2O.
• Magnetic data are analyzed within the framework of spin 1/2 dimer model.
• Singlet-triplet transition is captured employing quantum complementarity principle.
• Field dependent specific heat data also provides the signature of the transition.

Experimental realization of magnetic field induced singlet to triplet transition is reported for NH4CuPO4·H2O, a two spin cluster material with isotropic Heisenberg interaction. Experimental magnetization and specific heat data have been collected as a function of temperature and magnetic field. Experimental data have been analyzed in terms of Heisenberg dimer model. Two quantum complementary observables representing local and non-local properties of the spins are constructed using the experimental data and a clear evidence of singlet to triplet transition is observed through partial quantum information sharing when the magnetic field is swept through a particular value. Signature of this transition has also been captured when specific heat is measured as a function of magnetic field. Furthermore, using the experimental specific heat data, magnetic energy values are calculated and their variations are captured as a function of magnetic field and temperature.