K. Dorr et al., Large magnetoresistance of the polycrystalline metamagnetic layered manganite La1.2Nd0.2Sr1.6Mn2O7, J APPL PHYS, 87(2), 2000, pp. 814-816
Magnetization and magnetotransport have been investigated for polycrystalli
ne samples of the bilayer Ruddlesden-Popper compound La1.2Nd0.2Sr1.6Mn2O7 t
hat shows the colossal magnetoresistance effect connected with ferromagneti
c ordering at T-C=74 K. At T-2=38 K the compound reveals a transition from
the ferromagnetic to an antiferromagnetic spin arrangement of alternating f
erromagnetic bilayers, which undergoes a first order metamagnetic transitio
n towards ferromagnetism in a magnetic field of similar to 3.5 kOe at 20 K.
In measurements of resistance vs magnetic field, this transition is accomp
anied by a large resistance drop of [R(5 kOe)-R(0)]/R(0)=-60% at 5 K. The t
unneling-like magnetoresistance (MR) known for current transport perpendicu
lar to the layers in (La, Nd)(1.4)Sr1.6Mn2O7 single crystals contributes to
this large MR observed in a polycrystalline sample. While current is expec
ted to mainly follow the bilayers within the grains due to the anisotropy o
f conductivity, the high value of resistivity of our sample (similar to 8 O
mega cm at 5 K) suggests that current paths are partially directed perpendi
cular to the layers. (C) 2000 American Institute of Physics. [S0021-8979(00
)03102-9].