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Register a new userMagnetic behavior of nanocrystalline ErCo2
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Added by
E. V. Sampathkumaran
Publication date
2009
fields
Physics
and research's language is
English
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We have investigated the magnetic behavior of the nanocrystalline form of a well-known Laves phase compound, ErCo2 - the bulk form of which has been known to undergo an interesting first-order ferrimagnetic ordering near 32 K - synthesized by high-energy ball-milling. It is found that, in these nanocrystallites, Co exhibits ferromagnetic order at room temperature as inferred from the magnetization data. However, the magnetic transition temperature for Er sublattice remains essentially unaffected as though the (Er)4f-Co(3d) coupling is weak on Er magnetism. The net magnetic moment as measured at high fields, sat at 120 kOe, is significantly reduced with respect to that for the bulk in the ferrimagnetically ordered state and possible reasons are outlined. We have also compared the magnetocaloric behavior for the bulk and the nano particles.
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We report the results of ac and dc magnetic susceptibility (chi) and electrical resistivity (rho) measurements on the single crystals of Er2PdSi3, crystallizing in an AlB2-derived hexagonal structure, for two orientations H//[0001] and H//[2 -1 -1 0]. For H//[0001], there are apparently two magnetic transitions as revealed by the ac chi data, one close to 7 K attributable to antiferromagnetic ordering and the other around 2 K. However, for H // [2 -1 -1 0], we observe additional features above 7 K (near 11 and 23 K) in the plot of low-field chi(T); also, there is no corresponding anomaly in the rho(T) plot. In this respect, the magnetic behavior of this compound is novel, particularly while compared with other members of this series. The features in ac chi respond differently to the application of a small dc magnetic field for the two directions. As far as low temperature (T= 1.8 and 5 K) isothermal magnetization (M) behaviour is concerned, it exhibits meta-magnetic-like features around 2 kOe saturating at high fields for the former orientation, whereas for the latter, there is no saturation even at 120 kOe. The sign of paramagnetic Curie temperature is different for these two directions. Thus, there is a strong anisotropy in the magnetic behavior. However, interestingly, the rho(T) plots are found to be essentially isotropic, with the data revealing possible formation of magnetic superzone formation below 7 K.
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We report magnetic behavior of two intermetallics-based kagome lattices, Tb3Ru4Al12 and Er3Ru4Al12, crystallizing in the Gd3Ru4Al12-type hexagonal crystal structure, by measurements in the range 1.8-300 K with bulk experimental techniques (ac and dc magnetization, heat-capacity and magnetoresistance). The main finding is that the Tb compound, known to order antiferromagnetically below (T_N=) 22 K, shows glassy characteristics at lower temperatures (<15K), thus characterizing this compound as a re-entrant spin-glass. The data reveal that glassy phase is quite complex and is of a cluster type. Since the glassy behavior was not seen for the Gd analogue in the past literature, this finding for the Tb compound emphasizes that this kagome family could provide an opportunity to explore the role of higher order (such as quadrupole) in bringing out magnetic frustration. Additional findings reported here for this compound are: (i) The temperature dependence of magnetic susceptibility and electrical resistivity in the range 12 - 20 K are found to be hysteretic leading to a magnetic phase in this temperature range, mimicking disorder-induced first-order magnetic phase-transition. (ii) Features attributable to an interesting magnetic phase co-existence phenomenon in the magnetoresistance in zero field, after cycling across metamagnetic transition fields, are observed. With respect to the Er compound, we do not find any evidence for long-range magnetic ordering down to 2 K, but this appears to be on the verge of magnetic order at 2 K.
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