Aplicación de nuevas sondas microscópicas al estudio del magnetismo de las fases de laver RCO2

Abstract

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Parimagnetism in HoCo2and TmCo2

“…As has been discussed in previous works [1,9,51], the occurrence of parimagnetism in ErCo 2 is caused by competition of interactions on the Co sublattice. In particular, the Co-Co exchange interaction is responsible for the short-range order correlations, which induce the collective reversal of the Co moments at the temperature at which the net moment of the Co magnetic sublattice crosses zero.…”

Elastic and electrical anomalies at low-temperature phase transitions in BiFeO3

“…The DMA data also show a very weak anomaly, seen most clearly in the data for tan δ collected at 2 Hz (figure 2), at 140 K. The weakness of the 140 K feature and strength of the one around 200 K contrasts markedly with the relative scale of the features seen at these T s in the electromagnon spectra, which may indicate variable coupling between strain and the primary order parameter at the lower-T anomaly. Resonant ultrasonic spectroscopy of BiFeO 3 from ca 5 to 1000 K will be reported elsewhere [29]. These show strong anomalies near 1 MHz at 140 K, and in this sense are complementary to the low-frequency (several Hz) DMA measurements reported here, which give strong effects near 201 K but only weak 'shoulders' at 140 K. In addition, the RUS measurements confirm a glassy viscous state of between 30 and 50 K; note that the Vogel-Fulcher freezing temperature was previously estimated by Singh et al as 29.4 K and a peak in the magnetic susceptibility found at 50 K. Kleemann et al [30] have demonstrated ageing of magnetization in this spin-glass temperature regime.…”

Parimagnetism in RCo$_2$ series (R=Dy, Ho, and Tm)

“…As it has been discussed in previous works, 1,9,39 the occurrence of parimagnetism in ErCo 2 is due to a competition of interactions on the Co sublattice. In particular, the Co-Co exchange interaction is responsible for the short-range order correlations which facilitate the collective reversal of the Co moments at the temperature where the net moment of the Co magnetic sublattice crosses zero.…”