- Email: [email protected]
Growth of nickel manganite single crystals
Journal of Crystal Growth 1 (1967) 325—326 © North-Holland Publishing Co., Amsterdam
GROWTH OF NICKEL MANGANITE SINGLE CRYSTALS
H. MAKRAM C.N.R.S., Laboratoire de Magnétisme et de Physique du Solide, 92
—
Bellevue, France
Received 7 Juli 1967 A method for growing single crystals of NiMn,0
4 using Bi20,— B,03 as a flux is described. Chemical analysis indicated the presence of the phase NiMn2O4. The lattice constant, Curie tern-
The recent and the growing interest in the properties of adiscovery series offerrimagnetic spine! compounds Me2 + Mn~+ 04 where Me is a divalent metal ion such as Ni, Co, Mg, or Zn1’2 .3), suggest the desirability of obtaining single crystals of these materials in order that their fundamental properties could be completely understood. thishave study, and we describe in this note We the undertook technique we developed to prepare the single crystals from the fluxed melts. We have chosen nickel manganite, as a typical case for our study. The absence of phase equilibrium data for the system involved and the possible polyvalent state of Mn ions make the problem more difficult. This required the systematic study of several flux systems and controlled atmospheres applied during the crystal growth. The raw materials Mn0 1 365’ NiO and the flux cornponents were of reagent grade purity, The preliminary runs were carried out using the well known flux systems PbO—PbF2 and PbO—B203. The crystallization was done both in the air atmosphere, 2, in order and under pure oxygen pressure of 15 kg/cm to enhance the complete oxidation of manganese ions to the trivalent state. The choice of these flux systems was however unsuitable. We found indeed that the resulting phase was the lead manganite. This stable phase seems to prevent the crystallization of nickel manganite. The above result suggested the elimination of any lead salts from the flux system. In the second phase of the study, the flux system Bi203—B2O3 was used, When the crystallization was carried out under an
perature and magnetization agree well with values of polycrystalline material.
2, very few crystals of oxygen manganite pressure of 15 kg/cm nickel were obtained, but simultaneously the presence of a large quantity of prismatic shaped crystals was observed. These latter were found to be the compound BiMn 2O5 having an orthorhombic structure which crystallizes in the Pbam group cases, with cona= 4). In many 7.47 A; b = 8.52 A; c = 5.75 A clusions are supported by the results of chemical analysis. This result could be understood by the oxydation of some Ni and Mn ions to a valence state three and higher than three respectively. This indicated that the atmosphere applied was unfavourable for the crystallization of the desired nickel—manganese phase. On the contrary, the crystallization under the normal air pressure resulted in the yield of crystals in the form of regular octahedrons. Typical spinel-phase was found by X-ray examination and chemical analysis indicated this phase to be NiMn2O4. The crystals obtained were quite sound and flawless having linear dimensions up to 6 mm. No attempt was made to grow large crystals. A Btypical composition consisted of 56.7 Bi203, 13.3 203, 30 NiO and 30 Mn01365 the numbers indicating the mol %. The platinum crucible containing such a composition was heated to a soaking temperature of 1280 °C for a period of 60 hours, then was cooled to 860 °Cat a uniform rate of I °Cper hour. At this temperature the crucible was taken out and either water or air quenched. After the run the crucible was weighed with its contents, and the increase in weight corresponded well to an oxidation of Mn01 365 to Mn203. It is to be noted that heating for a long period comes
325
326
H. MAKRAM
from the fact that the reaction between Mn203 and NiO proceeds very slowly. However, if the crystallization begins too soon, Mn~O3is converted to Mn3O4 which reacts with a portion of the NiO and the resulting manganese-rich spine! phase shows very little tendency to absorb the remaining unreacted NiO3).and to regain simultaneously the lostofoxygen Qualitative measurements lattice content constant, Curie
liminary results indicate that the same method could be used for the preparation of other manganites as well. Acknowledgment TheEnaud author like to thank Mr. Duclos analand Mrs. of would this Laboratory for the chemical
ysis of the samples. temperature and magnetization of the crystals agreed well with the values published for polycrystalline ma- References terial5). The results of the study ofmagnetic anisotropy 1) P. K. Baltzer and J. G. White, J. Appi. Phys. 29 (1958) 445. and resonance linewidth of these crystals will be re- 2) K. S. Irani, A. P. B. Sinha and A. B. Biswas, J. Phys. Chem. Solids 23 (1962) 727. ported in a further publication. 3) E. G. Larson and R. J. Arnott, J. Phys. Chem. Solids 23 In conclusion, we have shown that nickel manganite (1962) 1771. single crystals can be successfully grown by the fluxed 4) E. F. Bertaut, G. Buisson, S. Quezel-Ambrunaz et G. Quezel, Solid State Commun. 5 (1967) 25. melt technique using the flux system Bi 203—B203. Pre- 5) G. Villers and R. Buhi, Compt. Rend. 260 (1965).
GROWTH OF NICKEL MANGANITE SINGLE CRYSTALS
H. MAKRAM C.N.R.S., Laboratoire de Magnétisme et de Physique du Solide, 92
—
Bellevue, France
Received 7 Juli 1967 A method for growing single crystals of NiMn,0
4 using Bi20,— B,03 as a flux is described. Chemical analysis indicated the presence of the phase NiMn2O4. The lattice constant, Curie tern-
The recent and the growing interest in the properties of adiscovery series offerrimagnetic spine! compounds Me2 + Mn~+ 04 where Me is a divalent metal ion such as Ni, Co, Mg, or Zn1’2 .3), suggest the desirability of obtaining single crystals of these materials in order that their fundamental properties could be completely understood. thishave study, and we describe in this note We the undertook technique we developed to prepare the single crystals from the fluxed melts. We have chosen nickel manganite, as a typical case for our study. The absence of phase equilibrium data for the system involved and the possible polyvalent state of Mn ions make the problem more difficult. This required the systematic study of several flux systems and controlled atmospheres applied during the crystal growth. The raw materials Mn0 1 365’ NiO and the flux cornponents were of reagent grade purity, The preliminary runs were carried out using the well known flux systems PbO—PbF2 and PbO—B203. The crystallization was done both in the air atmosphere, 2, in order and under pure oxygen pressure of 15 kg/cm to enhance the complete oxidation of manganese ions to the trivalent state. The choice of these flux systems was however unsuitable. We found indeed that the resulting phase was the lead manganite. This stable phase seems to prevent the crystallization of nickel manganite. The above result suggested the elimination of any lead salts from the flux system. In the second phase of the study, the flux system Bi203—B2O3 was used, When the crystallization was carried out under an
perature and magnetization agree well with values of polycrystalline material.
2, very few crystals of oxygen manganite pressure of 15 kg/cm nickel were obtained, but simultaneously the presence of a large quantity of prismatic shaped crystals was observed. These latter were found to be the compound BiMn 2O5 having an orthorhombic structure which crystallizes in the Pbam group cases, with cona= 4). In many 7.47 A; b = 8.52 A; c = 5.75 A clusions are supported by the results of chemical analysis. This result could be understood by the oxydation of some Ni and Mn ions to a valence state three and higher than three respectively. This indicated that the atmosphere applied was unfavourable for the crystallization of the desired nickel—manganese phase. On the contrary, the crystallization under the normal air pressure resulted in the yield of crystals in the form of regular octahedrons. Typical spinel-phase was found by X-ray examination and chemical analysis indicated this phase to be NiMn2O4. The crystals obtained were quite sound and flawless having linear dimensions up to 6 mm. No attempt was made to grow large crystals. A Btypical composition consisted of 56.7 Bi203, 13.3 203, 30 NiO and 30 Mn01365 the numbers indicating the mol %. The platinum crucible containing such a composition was heated to a soaking temperature of 1280 °C for a period of 60 hours, then was cooled to 860 °Cat a uniform rate of I °Cper hour. At this temperature the crucible was taken out and either water or air quenched. After the run the crucible was weighed with its contents, and the increase in weight corresponded well to an oxidation of Mn01 365 to Mn203. It is to be noted that heating for a long period comes
325
326
H. MAKRAM
from the fact that the reaction between Mn203 and NiO proceeds very slowly. However, if the crystallization begins too soon, Mn~O3is converted to Mn3O4 which reacts with a portion of the NiO and the resulting manganese-rich spine! phase shows very little tendency to absorb the remaining unreacted NiO3).and to regain simultaneously the lostofoxygen Qualitative measurements lattice content constant, Curie
liminary results indicate that the same method could be used for the preparation of other manganites as well. Acknowledgment TheEnaud author like to thank Mr. Duclos analand Mrs. of would this Laboratory for the chemical
ysis of the samples. temperature and magnetization of the crystals agreed well with the values published for polycrystalline ma- References terial5). The results of the study ofmagnetic anisotropy 1) P. K. Baltzer and J. G. White, J. Appi. Phys. 29 (1958) 445. and resonance linewidth of these crystals will be re- 2) K. S. Irani, A. P. B. Sinha and A. B. Biswas, J. Phys. Chem. Solids 23 (1962) 727. ported in a further publication. 3) E. G. Larson and R. J. Arnott, J. Phys. Chem. Solids 23 In conclusion, we have shown that nickel manganite (1962) 1771. single crystals can be successfully grown by the fluxed 4) E. F. Bertaut, G. Buisson, S. Quezel-Ambrunaz et G. Quezel, Solid State Commun. 5 (1967) 25. melt technique using the flux system Bi 203—B203. Pre- 5) G. Villers and R. Buhi, Compt. Rend. 260 (1965).