A projectile Coulomb-excitation experiment was performed at the radioactive-ion beam facility HIE-ISOLDE at CERN to obtain E2 and M1 transition matrix elements of 140Nd using the multistep Coulomb-excitation code GOSIA. The absolute M1 strengths, B(M1;2+2→2+1)=0.033(8)μ2N,B(M1;2+3→2+1)=0.26+0.11−0.10μ2N, and B(M1;2+4→2+1)<0.04μ2N, identify the 2+3 state as the main fragment of the one-quadrupole-phonon proton-neutron mixed-symmetry state of 140Nd. The degree of F-spin mixing in 140Nd was quantified with the determination of the mixing matrix element VF−mix<7+13−7keV.