A magnetic recording medium of the present invention includes a non-magnetic substrate, and a magnetic layer containing a magnetic powder. The magnetic powder is constituted by an ε-iron oxide powder. The magnetic layer has a squareness in a thickness direction of 0.65 or more. In a differential curve obtained by differentiating a hysteresis curve in the thickness direction of the magnetic layer, two or more peaks are present. In a case where, out of peaks in the same direction among the above-described peaks, a local maximum of a largest peak in a magnetic field range of +500 oersted [Oe] or more is taken as P1 and a local maximum of a largest peak in a magnetic field range of −500 oersted [Oe] or more and less than +500 oersted [Oe] is taken as P2, a relationship below is satisfied:

0.25≦P2/P1≦0.60.

A magnetic recording medium of the present invention includes a non-magnetic substrate, and a magnetic layer containing a magnetic powder. The magnetic powder is constituted by an ε-iron oxide powder. The magnetic layer has a squareness in a thickness direction of 0.65 or more. In a differential curve obtained by differentiating a hysteresis curve in the thickness direction of the magnetic layer, two or more peaks are present. In a case where, out of peaks in the same direction among the above-described peaks, a local maximum of a largest peak in a magnetic field range of +500 oersted [Oe] or more is taken as P1 and a local maximum of a largest peak in a magnetic field range of −500 oersted [Oe] or more and less than +500 oersted [Oe] is taken as P2, a relationship below is satisfied:

0.25≦P2/P1≦0.60.

In one embodiment, a method for forming a substantially monodisperse lubricant includes: providing a plurality of perfluoropolyether (PFPE) precursors, each PFPE precursor including two end segments and a PFPE backbone disposed therebetween; protecting one of the end segments of each PFPE precursor with one or more protecting agents to form a plurality of mono-protected PFPE precursors, each mono-protected PFPE precursor including a protected end segment and an unprotected end segment; and coupling the unprotected end segment of each of the mono-protected PFPE precursors to the unprotected end segment of another of the mono-protected PFPE precursors via a coupling agent to form multidentate PFPE structures. In another embodiment, a substantially monodisperse lubricant includes a plurality of multidentate perfluoropolyether (PFPE) structures, each multidentate PFPE structure including at least two end segments and a middle segment therebetween, wherein the multidentate PFPE structures have a molecular weight that is substantially the same.

The present invention relates to a phosphazene compound [compound (L)] comprising a cyclophosphazene central core wherein each phosphorus atom of said core bears a substituent independently selected from: a) a chain (A), said chain (A) comprising a (per)fluoropolyether chain [chain (R.sub.f)], one or more aromatic or heteroaromatic moieties [moiety/ies (Ar.sup.m)] and, optionally, one or more hydroxy groups and b) a chain (B), said chain (B) comprising a (per)fluoropolyether chain [chain (R.sub.f)] and one or more hydroxy groups with the proviso that at least one phosphorous atom of the central core is substituted with chain (A) and to mixtures of compounds (L). The invention further relates to methods for preparing compounds (L), to lubricant compositions comprising compounds (L) and to methods for lubricating magnetic recording media comprising applying a compound (L) or a lubricant compositions containing them to the surface of said medium.

Disclosed is a fluoropolyether compound comprising a C.sub.4-10 aliphatic hydrocarbon chain present in the middle of the fluoropolyether compound and at least two perfluoropolyethers.

The present invention relates to a device for magnetic recording that includes a storage medium having a media surface. The media surface has a plurality of lands and recesses between the lands. A polymer layer fills the recesses so that the media surface is substantially planar.

This fluorine-containing ether compound is a fluorine-containing ether compound represented by formula (1).

R.sup.1—X—R.sup.2—CH.sub.2—R.sup.3—CH.sub.2—R.sup.4  (1)

(In formula (1), R.sup.1 is an alkenyloxy group of 2 to 8 carbon atoms or an alkynyloxy group of 3 to 8 carbon atoms. R.sup.2 is represented by formula (2) shown below. In formula (2), a represents an integer of 1 to 3. X is represented by formula (3) shown below. In formula (3), b represents an integer of 1 to 5, Y is a divalent linking group that is bonded to a carbon atom in formula (2), and R represents an alkyl group of 1 to 6 carbon atoms or H. R.sup.3 represents a perfluoropolyether chain. R.sup.4 represents a terminal group containing two or three polar groups, wherein each polar group is bonded to a different carbon atom, and the carbon atoms to which the polar groups are bonded are bonded to each other via a linking group containing a carbon atom to which a polar group is not bonded.)

##STR00001##

A multidentate lubricant comprising an anchoring moiety Ra attached to a plurality of sidechain moieties —(Rb—Re) according to the general formula: Ra—(Rb—Re).sub.x; wherein Ra is a multivalent radical of valance x; and each sidechain includes a perfluoroethyl ether moiety. The lubricant can be used in conjunction with a magnetic recording medium and/or a magnetic data storage system.

A fluorine-containing ether compound represented by formula (1) shown below.
R.sup.4—CH.sub.2—R.sup.3—CH.sub.2—R.sup.2—CH.sub.2—R.sup.1—CH.sub.2—R.sup.2—CH.sub.2—R.sup.3—CH.sub.2—R.sup.4  (1)
(In formula (1), R.sup.1 and R.sup.3 represent different perfluoropolyether chains, R.sup.2 represents a linking group containing one or more polar groups, and R.sup.4 represents a terminal group containing two or more polar groups.)

A fluorine-containing ether compound represented by formula (1) shown below.
R.sup.4—CH.sub.2—R.sup.3—CH.sub.2—R.sup.2—CH.sub.2—R.sup.1—CH.sub.2—R.sup.2—CH.sub.2—R.sup.3—CH.sub.2—R.sup.4  (1)
(In formula (1), R.sup.1 and R.sup.3 represent different perfluoropolyether chains, R.sup.2 represents a linking group containing one or more polar groups, and R.sup.4 represents a terminal group containing two or more polar groups.)