Magnetic phase transitions in the NdFe3(BO3)4 multiferroic

Abstract

Low-temperature studies of the behavior of the sound velocity and attenuation of acoustic modes have been performed on a single crystal NdFe 3 (BO 3 ) 4 Transitions of the magnetic subsystem to the antiferromagnetically ordered state at T N ≈ 30.6 K have been revealed in the temperature behavior of the elastic characteristics. The features in the temperature behavior of elastic characteristics of the neodymium ferroborate and its behavior in the external magnetic field, applied in the basic plane of the crystal, permit us to suppose that the transition to an incommensurate spiral phase is realized in the system. This phase transition behaves as the first order one. H-T phase diagrams for the cases H || a and H || b have been constructed. The phenomenological theory, which explains observed features, has been developed.

Magnetooptical Study of Spin-Orientation Phase Transition in NdFe3(BO3)4 Single Crystal

“…In works [6,7], this method was applied for the first time to research the spin-orientation phase transition induced by the magnetic field in a NdFe 3 (BO 3 ) 4 crystal. The results obtained were confirmed by the data of resonance [8] and acoustic [9] studies of the crystal concerned.…”

Magnetic field-induced phase transitions in the antiferromagnet Nd0.6Dy0.4Fe3(BO3)4

“…First let us discuss the anomaly at T = 31.4 K. We observed analogous behavior of acoustic characteristics in NdFe 3 (BO 3 ) 4 [14] and in the binary compound Nd 0.75 Dy 0.25 Fe 3 (BO 3 ) 4 in the vicinities of the Néel temperature [5,6]. Thus, we can suppose according to the characteristic shape of that anomaly that in Nd 0.6 Dy 0.4 Fe 3 (BO 3 ) 4 the temperature 31.4 K is the magnetic ordering point.…”

“…The critical fields Н cr1 and Н cr2 are determined as average values between the positions of the anomalies in the velocity (attenuation) for growing and decrease of the value of the magnetic field. The example of the magnetic field dependence of the velocity and attenuation of the mode q || y, u || z for the lowest temperature of the experi-* It was determined earlier [12][13][14], that transverse modes demonstrate the brightest features in the behavior of the elastic characteristics of ferroborates. The effects in longitudinal modes are one order of magnitude weaker, and, hence, will not be analyzed here.…”

“…Anomalies in the behavior of elastic characteristics in the vicinities of magnetic phase transformations, as a rule, are very bright. It gives the opportunity to discover such transitions, and also to determine their kind often more reliably than with the help of other, even only magnetic methods [14]. This is why, the ultrasound studies of the compound Nd 0.6 Dy 0.4 Fe 3 (BO 3 ) 4 are in-time and actual.…”

Magnetoelastic properties of Nd0.9Dy0.1Fe3(BO3)4 ferroborate

“…Recall that recent neutron diffraction experiments show that a spontaneous realignment of the collinear EP magnetic structure into an incommensurate spiral structure takes place in single crystal Nd ferroborate below T ic ¼ 13 K. 11,12 In studying the magnetoelastic properties of NdFe 3 (BO 3 ) 4 we have observed a similar increase in the speed for all transverse modes in the range 10 K < T < 20 K, which was attributed specifically to a transition into a spiral magnetic phase. 10 Since Nd 0.9 Dy 0.1 Fe 3 (BO 3 ) 4 has a rather high (90%) neodymium content, while the EP ! EA spin reorientation takes place in it below 8 K, a realignment of the magnetic structure from collinear easy-plane to spiral is entirely possible.…”