Magnetotransport properties of flux melt grown single crystals of Co-substituted manganites with perovskite structure

Abstract

Single crystals of La1−xBaxMn1−yCoyO3 (0.26 ≤ x ≤ 0.37; 0 ≤ y ≤ 0.31) perovskites were grown by the flux melt technique using the BaO–B2O3–BaF2 ternary system as a solvent. It was found that the cobalt content in the crystals is determined by the average oxidized state of the manganese ions and depends nonlinearly on the molar ratio of Co/Mn in the initial mixture. All the crystals exhibit ferromagnetic behaviour at low temperatures as well as a jump of resistivity and a magnetoresistance peak around the Curie temperature, gradually decreasing as the cobalt content increases. The low-temperature ferromagnetic phase transforms from the metallic to the semiconducting state with increase in cobalt content.

Magneto-transport study of manganites (La0.75−xGdx)Ca0.25MnO3

“…Such a temperature variation of magnetic susceptibility is characteristic for solids with antiferromagnetic ordering of the gadolinium and manganese sublattices. This observation is consistent with a magnetic structure reported for the Gd 0.67 Ca 0.33 MnO 3 [5][6][7].…”

“…A strong role in magnetization reduction, played by a substitution of Gd ions onto the La sites, is also found both in magnitude and temperature variation of magnetization measured in static magnetic fields up to 6 T [5]. It is observed that the magnetization magnitude and the Curie temperature are monotonically suppressed when the Gd content x varies from 0 to 0.75.…”

“…The Curie temperatures determined by a maximum slope are equal to 93 and 82 K, when measured in magnetic field of 100 and 300 Oe, respectively. One may conclude that the energy barriers pinning the magnetization vectors for both the sublattices are considerably high since even the magnetic field of 6 T is not enough to achieve magnetic saturation of these polycrystalline samples [5]. The field cooled and zero field cooled magnetization curves start to diverge below 100 K, when measured in 100 and 300 Oe fields.…”

Magnetic field dependence of electrical resistivity in fine grain La0.75Ca0.25MnO3

“…7 for the zero and 8 T cases. One may see that the phonon conductivity is overwhelming in the manganite studied, which is typically observed in manganites and cobaltites [3,14]. It is worth noticing that the electron/polaron contribution considerably increases especially below 140 K, when passing from zero to 8 T magnetic field.…”

Ellipsometric Studies of NdMnO3Single Crystals

“…The ortho rho mbic sym metry was found for the space gro up and l atti ce pa ra meters nm , nm , nm . The (La Ba Mn Co O sing le crysta l gro wn fro m Ûux mel t [24] was chara cteri zed by a pseudo-cubi c crysta l structure ( 0 390 nm ) wi th sm all rho mb ohedra l di storti on (space gro up ) at 300 K. The singl e crysta l of (La Ca Co O wa s gro wn by a Ûoati ng zone techni que and was chara cteri zed by tri gona l sym metry (space gro up wi th l atti ce consta nts nm , nm i n hexag onal system setti ng s). Twi nni ng structure sim i lar to tha t i n La Sr Co O [20] wa s observed i n the i nvesti gated (La Ca )Co O sam pl e.…”