Cf. Chang et al., PRESSURE EFFECTS ON THE TRANSPORT AND MAGNETIC-PROPERTIES OF LA1.4SR1.6MN2O7, Physical review. B, Condensed matter, 58(18), 1998, pp. 12224-12229
The effects of external (hydrostatic) pressure and internal (chemical)
pressure on the transport and magnetic properties of the La1.4Sr1.6Mn
2O7 are investigated. Both metal-insulator transition temperature T-m
and Curie temperature T-C increase with the increase of external press
ure. In contrast, the T-m and T-C decrease with the increase of Ca con
tent in La-1.4(Sr1 - xCax)(1.6)Mn2O7 (x less than or equal to 0.3), wh
ere the internal pressure is supposed to be introduced. External press
ure enlarge the ferromagnetic metal phase through the pressure-enhance
d transfer interaction of the charge carriers. The Mn-O-Mn bond angle
remains almost unchanged with the increase of Ca content which is in s
harp contrast to the La1 - xSrxMnO3 system. The Mn-O(3) bond length is
decreased by the external pressure while increased by the internal pr
essure. It is interpreted that the opposite behaviors of T-m and T-C f
or external and internal pressures are due to the different variations
of Mn-O(3) bond length. All other results are discussed and compared
with those in the (La,Sr)MNO3 system. [S0163-1829(98)06642-9].