We explore quantum-thermodynamic effects in a phosphorous (P)-doped graphene monolayer subjected to biaxial tensile strain. Introducing substitutional P atoms in the graphene lattice generates a tunable spin magnetic moment controlled by the strain control parameter epsilon. This leads to a magnetic quantum phase transition (MQPT) at zero temperature modulated by epsilon. The system transitions from a magnetic phase, characterized by an out-of-plane sp3 type hybridization of the P-carbon (P-C) bonds, to a non-magnetic phase when these bonds switch to in-plane sp2 hybridization. Employing a Fermi-Dirac statistical model, we calculate key thermodynamic quantities such as the electronic entropy Se and electronic specific heat Ce. At finite temperatures, we find a MQPT extension characterized by Se and Ce, where both display a distinctive Lambda-shape profile as a function of epsilon. These thermodynamic quantities sharply increase up to epsilon = 5% in the magnetic regime, followed by a sudden drop at epsilon = 5.5%, transitioning to a linear dependence on epsilon in the nonmagnetic regime. This controllable magnetic-to-nonmagnetic switch offers potential applications in electronic nanodevices operating at finite temperatures.