Hirofumi Fujioka

Relation between crystal and magnetic structures of layered manganite La2-2xSr1+2xMn2O7 (0.30 ≤ x ≤ 0.50)

The magnetic phase diagram of La 2-2 x Sr 1+2 x Mn 2 O 7 (0.30 ≤ x ≤ 0.50) was reexamined from the point of view of the crystal structure, particularly the Jahn-Teller (JT) distortion Δ J T of Mn-O 6 octahedra, i.e., the ratio of the averaged apical Mn-O bond length to the equatorial Mn-O bond length. We have found that Δ J T decreases with increasing hole concentration x , while the canting angle between neighboring planes continuously increases from 0° (planar ferromagnet: 0.32 ≤ x ≤0.38) to 180° (A-type antiferromagnet (AFM): x =0.48). The dominance of the A-type AFM structure with the decrease of Δ J T can be ascribed to the change in the e g orbital state from d 3 z 2 - r 2 to d x 2 - y 2 .

Neutron-Diffraction Studies on the Magnetic Ordering Process in the Layered Mn Perovskite La2-2xSr1+2xMn2O7 (x = 0.40, 0.45 and 0.48).

Comprehensive neutron-diffraction studies on La 2-2 x Sr 1+2 x Mn 2 O 7 ( x =0.40,0.45 and 0.48) single crystals have revealed that the low-temperature magnetic phase consists of planar ferromagnetic (FM) and A-type antiferromagnetic (AFM) components, indicating a canted AFM ordering. Upon increasing the hole concentration x , the canting angle between planes changes from 6.3° (nearly planar FM) at x =0.40 to 180° (A-type AFM) at x =0.48, while the ordering temperature of the FM component, T C , decreases from 120xa0K to 0xa0K, correspondingly. We have also discovered that the A-type AFM ordering remains above T C and shows an anomalous exponential decrease to T N ∼200xa0K. This newly found intermediate A-type AFM phase may play a significant role in the enhancement of CMR effects in this layered Mn perovskite system.

Interplay of the CE-Type Charge Ordering and the A-Type Spin Ordering in Half-Doped Bilayer Manganite LaSr 2Mn 2O 7

We demonstrate that the 50% hole-doped bilayer manganite LaSr 2 Mn 2 O 7 exhibits CE-type charge- and spin-ordered states below T N, CO A =210 K and below T N CE ∼145 K, respectively. However, the volume fraction of the CE-type ordering is relatively small, and the system is dominated by the A-type spin ordering. The coexistence of the two types of ordering is essential to understand the transport properties, and it can be viewed as an effective phase separation between the metallic d ( x 2 - y 2 ) orbital ordering and the charge-localized d (3 x 2 - r 2 )/ d (3 y 2 - r 2 ) orbital ordering.

NEUTRON SCATTERING STUDIES ON MAGNETIC STRUCTURE OF THE DOUBLE-LAYERED MANGANITE LA2-2XSR1+2XMN2O7 (0.30 X 0.50)

Abstract Systematic powder diffraction studies have been carried out to establish the magnetic phase diagram of La 2−2 x Sr 1+2 x Mn 2 O 7 (LSMO327) in a wide hole concentration range (0.30≤ x ≤0.50), using the HERMES diffractometer. LSMO327 exhibits a planar ferromagnetic structure for 0.32≤ x ≤0.38 at low temperatures. A finite canting angle between planar magnetic moments on neighboring planes starts appearing around x ∼0.40 and reaches 180° (A-type antiferromagnet) at x =0.48. At x =0.30, on the contrary, the magnetic moments are aligned parallel to the c -axis.

Spin dynamical properties and orbital states of the layered perovskite La 2 − 2 x Sr 1 + 2 x Mn 2 O 7 ( 0.3 x 0.5 )

Low-temperature spin dynamics of the double-layered perovskite

Spin dynamical properties of the layered perovskite La1.2Sr1.8Mn2O7

{mathrm{La}}_{2ensuremath{-}2x}{mathrm{Sr}}_{1+2x}{mathrm{Mn}}_{2}{mathrm{O}}_{7}

Influence of Quasi-Bi-Stripe Charge Order on Resistivity and Magnetism in the Bilayer Manganite La2-2xSr1+2xMn2O7.

(LSMO327) was systematically studied in a wide hole concentration range

Examination of spin fluctuations within the MnO2 layers in a bilayer manganite La1.1Sr1.9Mn2O7

(0.3l~xl0.5).

Highly degenerate canted spin structure in bilayer manganite La1.1Sr1.9Mn2O7.

The spin-wave dispersion, which is almost perfectly two-dimensional, has two branches due to a coupling between layers within a double-layer. Each branch exhibits a characteristic intensity oscillation along the out-of-plane direction. We found that the in-plane spin stiffness constant and the gap between the two branches strongly depend on x. By fitting to calculated dispersion relations and cross sections assuming a Heisenberg model, we have obtained the in-plane

Reply to Comment by Battle,Rosseinsky and Radaelli

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