Low-temperature magnetoresistance of biaxially strained 24-nm-thick La$_{0.67}$Ca$_{0.33}$MnO$_3$ films

The lateral unit cell parameter in nanodimensional La$_{0.67}$Ca$_{0.33}$MnO$_3$ (LCMO) films grown on (001)-oriented LaAlO$_3$ substrates is significantly (approximately 4%) smaller than the value measured along the normal to the substrate plane. At $T <$ 140 K, the temperature dependence of the resistivity $\rho$ of LCMO films follows the relation $\rho$–$\rho$ ($T$ = 4.2 K) $\approx\rho_2(H)T^{4.5}$, where $\rho_2$ is independent of the temperature but decreases with increasing magnetic field $H$. It is shown that this decrease is related both to a decay of the spin waves in ferromagnetic domains and to the transformation of antiferromagnetic phase inclusions into ferromagnetic ones.