Enhanced ferromagnetism by adding electrons in triple-decker Gd-phthalocyanine

The electronic structures and magnetic properties of triple-decker Gd-phthalocyanine have been studied by using the HSE06 hybrid function method. The results show that triple-decker Gd-phthalocyanine is a small band gap semiconductor. Ferromagnetic coupling is unstable in neutral triple-decker Gd-phthalocyanine due to the small energy difference between the ferromagnetic and antiferromagnetic state. Additional electrons can enhance the energy difference; the largest for triple-decker Gd-phthalocyanine is 0.062 eV with two additional electrons per phthalocyanine ring. A larger energy difference can result in stable ferromagnetic coupling in triple-decker Gd-phthalocyanine. Analysis of the wave function distribution and electron density difference shows that the additional electrons will occupy the innermost conjugate ring. The innermost conjugate ring is filled by the additional two electrons per phthalocyanine ring. The more electrons that occupy the innermost conjugate ring, the more enhanced the p(z)-f exchange interaction is, which is the reason for the ferromagnetic coupling in triple-decker Gd-phthalocyanine. Thus, the ferromagnetic coupling of triple-decker Gd-phthalocyanine with two additional electrons per phthalocyanine ring is the most stable. The ferromagnetism of triple-decker Gd-phthalocyanine that is enhanced by the additional electrons has potential applications in organic spintronics.