Effect of disorder on the thermodynamic phase transition in ${\mathrm{La}}_{0.70}{\mathrm{Ca}}_{0.30}\mathrm{Mn}{\mathrm{O}}_3$

Thermodynamic analysis of the ferromagnetic phase transition at $T_C$ of Y-doped ${\mathrm{La}}_{0.70}{\mathrm{Ca}}_{0.30}\mathrm{Mn}{\mathrm{O}}_3$ reveals that the broad anomaly in the specific heat is consistent with a large pressure effect on $T_C$. This is discussed in terms of random local strain fields originating from a distribution of rare-earth ionic sizes that cause competition between double-exchange and superexchange interactions.

Figure 1

Magnetization for $x=0$ and 0.15 upon ZFC (warming) and FC (cooling) in magnetic fields 0.1, 0.5, and $5\mathrm{T}$.

Figure 2

(a) Linear thermal expansion $\Delta l∕l_0$ and (b) linear thermal-expansion coefficient $\mu \left(T\right)$. The inset reveals the critical behavior above and below $T_C$ for the doped sample (see the text).

Figure 3

Specific heat $C_P$ for both samples. The solid line depicts the predicted peak for $x=0.15$. The inset displays $C_P∕T$.

Figure 4

Temperature dependence of the real component of the magnetic susceptibility of $x=0.15$ (upon warming and cooling) at $100\mathrm{Oe}$ for several pressures. The inset shows the pressure dependence of $T_C$; lines are a polynomial fit.

Figure 5

$\mu T$ multiplied by the scaling factor $\lambda =3350$ as a function of temperature for $x=0.15$.