ELSEVIER Physica C 291 (1997) 17-24 A comparative study of irreversible magnetisation and pinning force density in(RE)Ba2Cu307_ ~ and some other high-T c compounds in view of a novel scaling scheme M. Jirsa *, L. Pfist Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, CZ-18040 Praha 8, Czech Republic Received 12 May 1997; revised 26 July 1997; accepted 26 July 1997 Abstract We examined an extended set of experimental data on scaling of the field dependencies of the critical current density js(B) and/or the related pinning force density F(B) as found in literature for various high-T c single crystals, mainly (RE)Ba2Cu307_ ~ (RE-= rare earth), exhibiting the fishtail effect. The js(B) and/or F(B) curves, normalised with respect to the corresponding (fishtail) maximum, are shown to obey the functional dependencies jsc(b) = bmexp[(m/n)(1 - b")] and f(bf) = b~ n+ Jexp{[(m + l)/m](1 - b~)} where b and bf, are the applied field values normalised with respect to position of the corresponding (fishtail) maximum, and Jsc and f are the normalised values of the critical current density, and pinning force density, respectively. A possible link between the presented phenomenological scaling scheme and the theory of collective pinning is discussed. Most of the analyzed data could be well fitted with rn set equal to l and n left as the only free parameter, n varied from 0.5 to 3.95 but most values fell into the interval (1,2). We point out that the value n = 3//2 in the middle of this interval is predicted by the collective pinning theory for the small bundle pinning regime. © 1997 Elsevier Science B.V. PACS: 74.60 Jg; 74.60 Ge 1. Introduction The "peak" effect, the still not well understood phenomenon resulting in an enhancement of the critical current density at higher fields and tempera- tures has in recent years attracted a particular inter- est. One of the reasons is a potential use in applica- tions, another one is that the "peak" effect can serve as a test probe of our understanding to mecha- * Corresponding author. Fax: +420 2 821227; e-mail: jirsa@fzu.cz nisms of the vortex pinning in high temperature superconductors. During recent years a large number of papers dealing with different aspects of this phe- nomenon has been published offering a good plat- form for generalisation. According to the shape of the magnetisation hysteresis loop (MHL), the high-T c materials can be divided into two main categories: those with the fishtail shape of the curve (typically (RE)BaECU3OT_ ~ (RE=rare earth, (RE)-123 and similar single crystals) [1-26] and those with the arrow-head shape (Y-124, BiSrCaCuO and other re- lated compounds) [27-40]. It is probably not only an 0921-4534/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PHS0921-4534(97)01661-4