Metamagnetism of itinerant d-electrons in Laves phase compounds Lu(Co_1-xAl_x)₂

Abstract

Representative first-order metamagnetic transitions with a large hysteresis have been observed for x<or=0.06. The transition field Hc for x=0.06 is 220 kOe at 4.2 K. Simple but strong ferromagnetism is found for x>0.12. A mixing state of ferromagnetic and paramagnetic states of Co is assumed for 0.06<or=x<or=0.12. The paramagnetic component in the state also exhibits the metamagnetic transition. By surveying the temperature dependence of metamagnetism, a boundary temperature of the first- and second-order metamagnetic transitions, and a first-order magnetic transition in thermomagnetic curves are found for the first time. In relation to the magnetic phase transitions the critical parameters T1 and H1 are introduced and discussed. Finally a magnetic phase diagram is presented.

First Order Metamagnetic Transition inHo2Ti2O7Observed by Vibrating Coil Magnetometry at Milli-Kelvin Temperatures

“…However, despite striking similarities in the magnetization of a wide range of MMTs their microscopic origin may be radically different (see e.g. [1][2][3][4][5][6]). A prominent example of such a MMT has been reported recently for Dy 2 Ti 2 O 7 , where the transition is preceded by a plateau in the magnetization and a critical end-point is located at T m ∼ 0.36 K and B m ∼ 0.9 T for fields strictly parallel to a 111 axis [7,8].…”

Charge Disproportionation and Complex Magnetism in a PbMnO3 Perovskite Synthesized under High Pressure

“…A field-induced magnetic transition to a FM phase onsets at a critical field H cm1 of 2700 Oe and terminates at ∼3 T. This transition resembles a metamagnetism for itinerant electrons postulated by Wohlfarth and Rhodes . Examples of metamagnetism have been reported in Lu­(Co 0.94 Al 0.06 ) 2 (the inset in Figure a) and ZrZn 2 at a critical pressure where the ferromagnetism is suppressed . If we leave out the wing from the virgin state (point A) to 9 T, the rest of the M ( H ) loop, as shown in Figure b, exhibits a typical butterfly-shaped magnetization that has been observed in a molecular ferric wheel (MFW) NaFe 6 (the inset in Figure b).…”

“…(a) Magnetization of PbMnO 3 at 1.8 K; the definition of critical field H cm1 for the metamagnetism transition is shown in the figure. The inset: magnetization of Lu­(Co 0.94 Al 0.06 ) 2 (the data are after) and (b) same as (a) without the wing from the virgin state. The inset: magnetization of the MFW NaFe 6 (the data are after).…”

Relationship between the magnetic moment of Lu and the magnetic behavior of(YyLu1−y)(Co1−x<

“…In the case of Lu͑Co 1−x Al x ͒ 2 the critical Al concentration for the onset of ferromagnetism has been previously reported to be within the range 0.06 Յ x Յ 0.1. 6,20 However, recent studies have shown that the onset of ferromagnetism strongly depends on annealing due to the coexistence of paramagnetic and ferromagnetic states of Co atoms for x Շ 0.08. 19,32 Therefore, we have focused our study on the x = 0.1 compound for which the maximum Co within this series occurs.…”

“…Indeed, the Lu͑Co 1−x Al x ͒ 2 compounds show SFM behavior for the same concentration at which the Y͑Co 1−x Al x ͒ 2 compounds become WFMs. 12,18,20 Moreover, by contrast to the Y case, the Lu͑Co 1−x Al x ͒ 2 systems exhibit a sharp metamagnetic transition without showing a remarkable change in magnitude of the field-induced moment. 19,21 In the case of the ͑Y 1−y Lu y ͒͑Co 0.88 Al 0.12 ͒ 2 compounds it was found that the magnetic ground state changes from WFM ͑in Y-rich com-pounds͒ to SFM ͑in Lu-rich compounds͒ within a narrow concentration range in the vicinity of y = 0.4.…”