Abstract:We report on the synthesis and magnetic properties of frustrated Na0.22MnO2·0. 39H2O and K0.6MnO2·0.48H2O with the birnessite structure. The structure, static and dynamic magnetic properties of the compounds are investigated in detail. A combination of DC and AC magnetic susceptibility measurements and magnetization decay measurements reveal cluster glass behavior below the freezing temperature of 4 K for Na-birnessite and 6 K for K-birnessite. The frequency dependence of the freezing temperature is analyzed… Show more
“…Similar behavior was previously shown for bulk K 0.6 MnO 2 Á 0.48H 2 O with the birnessite structure. 14 The lowest temperature feature corresponds to surface water evaporation with a mass loss of 3.6% and according to the time derivative of the TG curve (DTG), the loss of water is completed at 97 1C with the maximum of the DSC curve at 77 1C. The second endothermic effect with a sharp maximum in the DSC curve at 149 1C corresponds to the release of interlayer crystal water with a further mass loss of 5.8%.…”
Section: Determination Of Chemical Compositionmentioning
confidence: 99%
“…However, we were unable to confirm the origin of these magnetic clusters. 14 Stacking faults involving the arrangement of MnO 6 octahedra could certainly enhance the magnetic frustration of the triangular magnetic lattice. Furthermore, we expect that the charge ordered regions of Mn 3+ and Mn 4+ ions can have a significant influence on the magnetic properties.…”
Section: Influence Of Structural Modulation On Magnetic Propertiesmentioning
confidence: 99%
“…46 However, the presence of Mn 4+ can suppress the Jahn-Teller distortion and lead to a low-spin Mn 3+ state in layers that have mixed-valent character. 14 In addition, layers containing only Mn 4+ can exhibit ferromagnetic Mn 4+ -O-Mn 4+ superexchange. 47 These different regions with different exchange mechanisms are likely manifested in the magnetic properties as cluster glass behavior.…”
Section: Influence Of Structural Modulation On Magnetic Propertiesmentioning
confidence: 99%
“…Cluster glass behavior was revealed below the freezing temperature of 4 K for sodium birnessite and 6 K for potassium birnessite. 14 Only one earlier study had been performed, on water-containing sodium birnessite, but this investigation was complicated by the presence of impurities of other magnetic phases. 21 No information is available on the magnetic properties of other A x MnO 2 ÁyH 2 O birnessites.…”
Section: Introductionmentioning
confidence: 99%
“…13 In contrast, relatively few studies have been reported on the magnetic properties of birnessites. 14 Accumulated experience from other layered materials provides a solid foundation for starting an investigation of the potentially unique magnetic behavior of birnessite compounds, where magnetic and non-magnetic layers alternate. Modifying the interlayer distance and the composition of the interlayer species by different topotactic reactions can affect the ratio of Mn 3+ /Mn 4+ , allowing tuning of the magnetic exchange and anisotropy along the stacking direction.…”
The largest single crystals of potassium birnessite thus far reported are grown. The structure is studied at atomic resolution. Mn3+/Mn4+ charge ordering, structural modulation and stacking faults are found.
“…Similar behavior was previously shown for bulk K 0.6 MnO 2 Á 0.48H 2 O with the birnessite structure. 14 The lowest temperature feature corresponds to surface water evaporation with a mass loss of 3.6% and according to the time derivative of the TG curve (DTG), the loss of water is completed at 97 1C with the maximum of the DSC curve at 77 1C. The second endothermic effect with a sharp maximum in the DSC curve at 149 1C corresponds to the release of interlayer crystal water with a further mass loss of 5.8%.…”
Section: Determination Of Chemical Compositionmentioning
confidence: 99%
“…However, we were unable to confirm the origin of these magnetic clusters. 14 Stacking faults involving the arrangement of MnO 6 octahedra could certainly enhance the magnetic frustration of the triangular magnetic lattice. Furthermore, we expect that the charge ordered regions of Mn 3+ and Mn 4+ ions can have a significant influence on the magnetic properties.…”
Section: Influence Of Structural Modulation On Magnetic Propertiesmentioning
confidence: 99%
“…46 However, the presence of Mn 4+ can suppress the Jahn-Teller distortion and lead to a low-spin Mn 3+ state in layers that have mixed-valent character. 14 In addition, layers containing only Mn 4+ can exhibit ferromagnetic Mn 4+ -O-Mn 4+ superexchange. 47 These different regions with different exchange mechanisms are likely manifested in the magnetic properties as cluster glass behavior.…”
Section: Influence Of Structural Modulation On Magnetic Propertiesmentioning
confidence: 99%
“…Cluster glass behavior was revealed below the freezing temperature of 4 K for sodium birnessite and 6 K for potassium birnessite. 14 Only one earlier study had been performed, on water-containing sodium birnessite, but this investigation was complicated by the presence of impurities of other magnetic phases. 21 No information is available on the magnetic properties of other A x MnO 2 ÁyH 2 O birnessites.…”
Section: Introductionmentioning
confidence: 99%
“…13 In contrast, relatively few studies have been reported on the magnetic properties of birnessites. 14 Accumulated experience from other layered materials provides a solid foundation for starting an investigation of the potentially unique magnetic behavior of birnessite compounds, where magnetic and non-magnetic layers alternate. Modifying the interlayer distance and the composition of the interlayer species by different topotactic reactions can affect the ratio of Mn 3+ /Mn 4+ , allowing tuning of the magnetic exchange and anisotropy along the stacking direction.…”
The largest single crystals of potassium birnessite thus far reported are grown. The structure is studied at atomic resolution. Mn3+/Mn4+ charge ordering, structural modulation and stacking faults are found.
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