H. Kuwahara

Current switching of resistive states in magnetoresistive manganites

Magnetoresistive devices (based on, for example, magnetic multilayers) exhibit large changes in electrical resistance in response to a magnetic field, which has led to dramatic improvements in the data density and reading speed of magnetic recording systems. Manganese oxides having a perovskite structure (the so-called manganites) can exhibit a magnetoresistive response that is many orders of magnitude larger than that found for other materials, and there is therefore hope that these compounds might similarly be exploited for recording applications. Here we show that the switching of resistive states in the manganites can be achieved not only by a magnetic field, but also by an electric field. For manganites of the form Pr1−xCaxMnO3, we find that an electrical current (and by implication a static electric field) triggers the collapse of the low-temperature, electrically insulating charge-ordered state to a metallic ferromagnetic state. We suggest that such a phenomenon could be exploited to pattern conducting ferromagnetic domains within an insulating antiferromagnetic matrix, and so provide a route for fabricating micrometre- or nanometre-scale electromagnets.

A First-Order Phase Transition Induced by a Magnetic Field

An electronic (metal-to-insulator) phase transition of the first order, which can be caused by an external magnetic field, was discovered in Nd1/2Sr1/2MnO3. A clear hysteresis was observed during the increase and decrease of an external magnetic field at a fixed temperature. The hysteretic field region was observed to depend critically on temperature and to drastically expand with a decrease of temperature, perhaps as a result of suppression of the effect of thermal fluctuations on the first-order phase transition. Although it has seldom been observed, this is thought to be a generic feature of the first-order phase transition at low temperatures near 0 kelvin.

Interplane Tunneling Magnetoresistance in a Layered Manganite Crystal

The current-perpendicular-to-plane magnetoresistance (CPP-MR) has been investigated for the layered manganite, La2−2xSr1+2xMn2O7 (x = 0.3), which is composed of the ferromagnetic-metallic MnO2 bilayers separated by nonmagnetic insulating block layers. The CPP-MR is extremely large (104 percent at 50 kilo-oersted) at temperatures near above the three-dimensional ordering temperature (Tc ≈ 90 kelvin) because of the field-induced coherent motion between planes of the spin-polarized electrons. Below Tc, the interplane magnetic domain boundary on the insulating block layer serves as the charge-transport barrier, but it can be removed by a low saturation field, which gives rise to the low-field tunneling MR as large as 240 percent.

Hole-concentration-induced transformation of the magnetic and orbital structures in Nd 1 − x Sr x MnO 3

We have peformed neutron diffraction measurements on melt-grown polycrystalline samples of

Orbital-State-Mediated Phase-Control of Manganites

{\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}

Striction-Coupled Magnetoresistance in Perovskite-Type Manganese Oxides

(0.49l~xl~0.75).

Critical change of magnetoresistance with bandwidth and doping in perovskite manganites

A systematic transformation of the crystalline and magnetic structures of this system was observed. This can be consistently explained by the change of the character of the Mn

Reentrant Transition of the Charge-Ordered State in Perovskite Manganites

{e}_{g}

Charge/orbital ordering in perovskite manganites

orbitals. When increasing X, the