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Synthesis and magnetic properties of single-crystalline Na2-xMn8O16 nanorods.

Lan C, Gong J, Liu S, Yang S - Nanoscale Res Lett (2011)

Bottom Line: The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time.The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures.The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanjing National Laboratory of Microstructures and Department of Physics, Nanjing University, 22 Hankou Road, Nanjing, 210093, China. sgyang@nju.edu.cn.

ABSTRACT
The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time. The nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a superconducting quantum interference device magnetometer. The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures. The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

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XRD pattern of Na2-xMn8O16 nanorods at room temperature.
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Figure 1: XRD pattern of Na2-xMn8O16 nanorods at room temperature.

Mentions: The X-ray diffraction (XRD) pattern of Na2-xMn8O16 nanorods is shown in Figure 1. The peaks can be indexed to monoclinic phase of Na2-xMn8O16 (JCPDS No. 42-1347). No secondary phase is observed, indicating pure phase Na2-xMn8O16 was obtained. As the Na+ cation is on the small side to stabilize the 2 × 2 tunnels compared with K+ cation, it is difficult to synthesize Na2-xMn8O16 [3]. In fact, we have tried to synthesize Na2-xMn8O16 by solid state reaction using stoichiometric amount of NaNO3 and MnCO3 as starting materials (suppose x = 0 in the formula Na2-xMn8O16), but no Na2-xMn8O16 phase could be obtained. In order to keep the 2 × 2 tunnel structure stable when K+ cations are replaced by Na+ cations, more Na+ cations are needed. In the high-temperature liquid molten salt, there is a large quantity of free Na+ cations. Suppose the unstable 2 × 2 tunnels formed in the molten salt first, then the Na+ cations can go into the tunnels. The excess of Na+ cations can guarantee there are enough Na+ cations in the 2 × 2 tunnels to make the tunnels stable. Based on the above discussion, the x in NaxMn8O16 should be larger than that in KxMn8O16. The x in KxMn8O16 is 1.5 [14], while the x in NaxMn8O16 obtained from the EDS result discussed later in this letter is 1.74, which confirms the above conclusion.


Synthesis and magnetic properties of single-crystalline Na2-xMn8O16 nanorods.

Lan C, Gong J, Liu S, Yang S - Nanoscale Res Lett (2011)

XRD pattern of Na2-xMn8O16 nanorods at room temperature.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211180&req=5

Figure 1: XRD pattern of Na2-xMn8O16 nanorods at room temperature.
Mentions: The X-ray diffraction (XRD) pattern of Na2-xMn8O16 nanorods is shown in Figure 1. The peaks can be indexed to monoclinic phase of Na2-xMn8O16 (JCPDS No. 42-1347). No secondary phase is observed, indicating pure phase Na2-xMn8O16 was obtained. As the Na+ cation is on the small side to stabilize the 2 × 2 tunnels compared with K+ cation, it is difficult to synthesize Na2-xMn8O16 [3]. In fact, we have tried to synthesize Na2-xMn8O16 by solid state reaction using stoichiometric amount of NaNO3 and MnCO3 as starting materials (suppose x = 0 in the formula Na2-xMn8O16), but no Na2-xMn8O16 phase could be obtained. In order to keep the 2 × 2 tunnel structure stable when K+ cations are replaced by Na+ cations, more Na+ cations are needed. In the high-temperature liquid molten salt, there is a large quantity of free Na+ cations. Suppose the unstable 2 × 2 tunnels formed in the molten salt first, then the Na+ cations can go into the tunnels. The excess of Na+ cations can guarantee there are enough Na+ cations in the 2 × 2 tunnels to make the tunnels stable. Based on the above discussion, the x in NaxMn8O16 should be larger than that in KxMn8O16. The x in KxMn8O16 is 1.5 [14], while the x in NaxMn8O16 obtained from the EDS result discussed later in this letter is 1.74, which confirms the above conclusion.

Bottom Line: The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time.The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures.The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanjing National Laboratory of Microstructures and Department of Physics, Nanjing University, 22 Hankou Road, Nanjing, 210093, China. sgyang@nju.edu.cn.

ABSTRACT
The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time. The nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a superconducting quantum interference device magnetometer. The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures. The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

No MeSH data available.


Related in: MedlinePlus